Theres only a built-in portal for MyBB currently, not sure in the future.
[Wiki: Portal] (Broken link, head over to docs.mybb.com instead)
to get your mybb portal.php go to your fourm domain
eg
www.mysite.com/fourm/portal.php
nd to set it as you fourm home page change the url to the o bother
in the acp
hope this helps