Participating in a social group forum is a bit tricky, because you can't post to that forum until you become a member of the related social group.
So to become a member of the social group first, you click on the "Social Groups" menu item which takes you to a listing of all of our member-created social groups:
http://forums.psychcentral.com/groups/
Browse through them or use the search box to find the one you're looking for. Click on the name of it to read more about it or to join it.
The "Join this group" option is
all the way at the bottom of the social group's page, which many people miss finding. Scroll down and then you'll see it in a blue bar (in the default theme).
Once you join a group, you will be able to post to that group's forum. Some groups may need that group leader's approval to join, so you may not be able to immediately post until the leader has approved your join request.
Hope that clarifies things....
DocJohn