I don't believe the instructions are very clear.
It says:
Install:
-Upload the contents of the upload folder
-Import product-gcbos.xml
-Set usergroup permissions
-Insert <!-- {SHOUTBOX} --> into the template you want it to display in (EG FORUMHOME, FORUMDISPLAY) or at the bottom of nabber
I found and assume FORUMHOME is the main "home" page, and FORUMDISPLAY is your "forum" tree in the styles and templates section.
With that said, where in the template are you supposed to place <!-- {SHOUTBOX} -->?