Okay, go to your messages. You will see the friend invite. You should have the option to "accept" or "decline" invitation. If you click accept then they are added to your friends and you to theirs.
If you want to send a friend invite...go to their homepage. Under their profile picture you will see a link saying, "Invite as friend", click on it and follow the directions. They will have to "accept" your invitation.
Go to a member's profile page.
To the right of their profile picture, you will see two links: 'Send a message' and 'Invite as friend'.
Click the 'Invite as friend' link.
The next page will allow you to add a note to your invitation.
Click the 'Send Message' button when you are done.
Once the member has accepted your friend invitation, they will be listed in your Friends widget.