Joining A Group
Some of the groups are "open" (meaning that anyone can join and view their content) whereas some are "closed" (meaning that the administrators have to approve your request to join). Once you click the group of interest, you can visit the public page of the group (it could be different than the page that the members can see) and can ask to join the group by clicking the respective button located below the group's name.
Once you join a group, you will receive announcements from this group in your “Home” page (first tab on the gray navigation bar). The group may post announcements, files, photos, documents, or send other notifications. Depending on the nature of the group, the administrator may allow all members to post content or restrict posting to a selected few. All activity of the group will show up on your “Home” page.