How to put some categories in the header menu?

<%@ Control Language="C#" AutoEventWireup="true" Inherits="NopSolutions.NopCommerce.Web.Modules.HeaderMegaMenu"
    CodeBehind="HeaderMegaMenu.ascx.cs" %>

<script type="text/javascript" src="<%=CommonHelper.GetStoreLocation()%>Scripts/jquery.megamenu.js"></script>
    <script type="text/javascript">
        //jkmegamenu.definemenu("anchorid", "menuid", "mouseover|click")
        jkmegamenu.definemenu("megaanchor", "megamenu1", "mouseover");
    </script>

<li><a href="" id="megaanchor"><%=GetLocaleResourceString("Category.Categories")%></a></li>
<%--Mega Menu--%>
<!--Mega Drop Down Menu HTML. Retain given CSS classes-->
<div id="megamenu1" class="megamenu">
    <div class="column">
        <h3><%=GetLocaleResourceString("Category.Categories")%></h3>
        <ul>
            <asp:PlaceHolder runat="server" ID="phCategories" EnableViewState="false" />
        </ul>
    </div>
    <div class="column">
        <h3><%=GetLocaleResourceString("Manufacturer.Manufacturers")%></h3>

        <asp:Repeater ID="rptrManufacturers" runat="server" OnItemDataBound="rptrManufacturers_ItemDataBound" EnableViewState="false">
            <HeaderTemplate>
                <ul>
            </HeaderTemplate>
            <ItemTemplate>
                <li>
                    <asp:HyperLink ID="hlManufacturer" runat="server" Text='<%#Server.HtmlEncode(Eval("LocalizedName").ToString()) %>'
                        CssClass='<%# ((int)Eval("ManufacturerId") == this.ManufacturerId) ? "active" : "inactive" %>' />
                </li>
            </ItemTemplate>
            <FooterTemplate>
                </ul>
            </FooterTemplate>
        </asp:Repeater>
        <div class="viewall">
            <a href="<%=CommonHelper.GetStoreLocation()%>manufacturers.aspx">
                <%=GetLocaleResourceString("Manufacturer.ViewAll")%></a>
        </div>
    </div>
    <br style="clear: left" />
    <!--Break after 3rd column. Move this if desired-->
    <br />
</div>
<%--@Mega Menu--%>

namespace NopSolutions.NopCommerce.Web.Modules
{
    public partial class TopicControl: BaseNopFrontendUserControl
    {
        private bool ValidatePassword()
        {
            bool passwordOK = true;
            if (this.Topic != null)
            {
                if (this.Topic.IsPasswordProtected &&
                    !this.Topic.Password.Equals(this.EnteredPassword))
                {
                    passwordOK = false;
                }
            }
            return passwordOK;
        }

        protected void btnPassword_OnClick(object sender, EventArgs e)
        {
            this.EnteredPassword = txtPassword.Text;
            bool passwordOK = ValidatePassword();
            if (!passwordOK)
            {
                lError.Text = GetLocaleResourceString("TopicPage.WrongPassword");
            }
            BindData();
        }

        private void BindData()
        {
            if (this.LocalizedTopic != null)
            {
                bool passwordOK = ValidatePassword();
                if (passwordOK)
                {
                    phPassword.Visible = false;
                    lTitle.Visible = true;
                    lBody.Visible = true;

                    if (!string.IsNullOrEmpty(this.LocalizedTopic.Title))
                    {
                        lTitle.Text = Server.HtmlEncode(this.LocalizedTopic.Title);
                    }
                    else
                    {
                        lTitle.Visible = false;
                    }
                    if (!string.IsNullOrEmpty(this.LocalizedTopic.Body))
                    {
                        lBody.Text = this.LocalizedTopic.Body;
                    }
                    else
                    {
                        lBody.Visible = false;
                    }
                }
                else
                {
                    phPassword.Visible = true;
                    lTitle.Visible = false;
                    lBody.Visible = false;
                }
            }
            else
            {
                this.Visible = false;
            }
        }
        
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            this.BindData();

            if (this.LocalizedTopic != null)
            {
                if (this.OverrideSEO)
                {
                    //title
                    string title = this.LocalizedTopic.MetaTitle;
                    if (String.IsNullOrEmpty(title))
                        title = this.LocalizedTopic.Title;
                    if (!string.IsNullOrEmpty(title))
                        SEOHelper.RenderTitle(this.Page, title, true);

                    //meta
                    if (!String.IsNullOrEmpty(this.LocalizedTopic.MetaDescription))
                        SEOHelper.RenderMetaTag(this.Page, "description", this.LocalizedTopic.MetaDescription, true);
                    if (!String.IsNullOrEmpty(this.LocalizedTopic.MetaKeywords))
                        SEOHelper.RenderMetaTag(this.Page, "keywords", this.LocalizedTopic.MetaKeywords, true);
                }
            }
        }

        protected override void OnPreRender(EventArgs e)
        {
            //default button
            this.txtPassword.Attributes.Add("onkeydown", "if(event.which || event.keyCode){if ((event.which == 13) || (event.keyCode == 13)) {document.getElementById('" + btnPassword.ClientID + "').click();return false;}} else {return true}; ");

            base.OnPreRender(e);
        }

        private LocalizedTopic localizedTopic = null;
        public LocalizedTopic LocalizedTopic
        {
            get
            {
                if (localizedTopic == null)
                {
                    localizedTopic = this.TopicService.GetLocalizedTopic(this.TopicName, NopContext.Current.WorkingLanguage.LanguageId);
                }
                return localizedTopic;
            }
        }

        public Topic Topic
        {
            get
            {
                if (this.LocalizedTopic != null)
                    return this.LocalizedTopic.Topic;
                else
                    return null;
            }
        }

        public string TopicName
        {
            get
            {
                object obj2 = this.ViewState["TopicName"];
                if (obj2 != null)
                    return (string)obj2;
                else
                    return string.Empty;
            }
            set
            {
                this.ViewState["TopicName"] = value;
            }
        }

        [DefaultValue(true)]
        public bool OverrideSEO
        {
            get
            {
                object obj2 = this.ViewState["OverrideSEO"];
                if (obj2 != null)
                    return (bool)obj2;
                else
                    return true;

            }
            set
            {
                this.ViewState["OverrideSEO"] = value;
            }
        }

        public string EnteredPassword
        {
            get
            {
                object obj2 = this.ViewState["EnteredPassword"];
                if (obj2 != null)
                    return (string)obj2;
                else
                    return string.Empty;
            }
            set
            {
                this.ViewState["EnteredPassword"] = value;
            }
        }
    }
}