The mods go in the HTML templates. Go to HTML Templates> Manage HTML> whatever bit you want to stick the mods in. For example, the Banner goes in Global HTML Elements > Board Header. Or if you wanna stick something right at the bottom of the index page, it's in Board Index Sections > +page bottom links. You will get the hang of it eventually, just have a poke around your HTML, but make sure you keep track of what you insert/delete
