nopCommerce 2.40 how to add new property to product

I know there is a help here:https://www.nopcommerce.com/docs/73/updating-an-existing-entity-how-to-add-a-new-property.aspx

The problem is I want to add to the Product table and it seems much more than that.
Also can I add the property after I added few products to my table or do I have to remove all products and then only I can add a column?

My ultimate goal is to have some kind of property which is boolean and then in index.cshtml have foreach loop to go through all products and add products in my Nivoslider. Admin can choose that this product needs to be added to slider.

I hope it is clear. If not please reply. Any help will be appreciated.

You can add a new column to your Products table and leave the existing entries there.  You just need to make the column nullable or supply a default value that will get applied to the ones already there.