To invite friends, tap the “Invite a friend” button in the overview.

You will be taken to a screen which allows you to lookup the person you want to invite. You can invite another user by (Make a Friend) username, email or Facebook.

You can also decide which friendship status to start with. When inviting, you probably want to start the friendship at “Friends” or “Good Friends”.

If you tap “Invite”, the system will lookup the invited user and send an invitation from you to this user.