Did you customize your project at all?
Does the rich editor appear on any other pages, or nowhere on your site?
Can you confirm that the code is correct?
--go to /Administration/Views/Catagory/_CreateOrUpdate.cshtml
at approximately line number 87
@Html.EditorFor(model => model.Locales[item].Description, "RichEditor")
Do you see that line?
In the settings, you can configure the following:
adminareasettings.richeditoradditionalsettings
adminareasettings.richeditorallowjavascript
adminareasettings.usericheditorinmessagetemplates
..but by default you should be seeing the rich editor.
Maybe try setting this setting to TRUE:
adminareasettings.usericheditorinmessagetemplates
then go check your one of your message templates and see if the rich editor appears.
If it does not, then you at least know you are probably just missing a file in your installation.