Hm, I never did anything with JFusion, nor do I have the possibility to test this, but
Table prefix: is probably the prefix for the Database-Tables of the Forum, you want to bridge (i.e. vb_ for vbulletin)
Cookie Path: is the Path for the bridged forum's Cookies (i.e.
www.yourdomain.com/forum
)
Full path: probably something like /var/www/site1234/forum