You edit the main page the same way you edit any other page. The only difference is that some wikis use the column tags to divide the page into columns. While these tags can be used on any page, they were designed with the main page in mind. Using them on the main page is not a requirement.
To edit those templates, simply go to the right side of the edit window. Underneath the categories, there'll be "show templates used on the page" (or some such). If you click it, you can go to the templates (or what you apparently call, "community tags") and edit its contents.