The swap forum is a user group that you must join in order to be able to post.
Hopefully, you can read
this post and get the instructions.
If not, on the left of the site are some links in boxes. Under "around the site" click on "
join a group." Select the radio button for swap hostesses and participants, click join group. There will be a delay because one of the site's (volunteer) moderator has to approve your request.