The Membership tool in My Workspace is where you can join available worksites.
Sites: On the Membership tool page, you'll see a list of all the worksites to which you belong. This includes sites you have joined, and sites that you have been added to as a participant by the creator of the site.
Joinable Sites: The
Joinable Sites link will
display a listing of available sites that you haven't joined. You can
Join for any of these sites.