If you want to begin adding people to your iMobster crew then you need to start on the Home tab found on the bottom task bar. Go to My Mob, which is located at the top of the right hand column in the middle of the Home display. When you select My Mob you will be given a number of options for adding people to your mob. The top one is to invite someone specifically by their five digit mob code, which is what you will do most likely.
Every iMobsters player has their own and when you enter it into the invite box they will then receive a message next time they log into iMobsters. From here, they can determine whether they will accept or decline. My Mob Code is N3Q14, and I accept all invitations as it serves you well to add people to your mob indiscriminately.
Below the Mob Code option is one to invite people by their cell phone number or email. Make sure before doing this that they actually have an iPhone and if they are already playing iMobsters. Once you send them the invite they will receive an invite code. When they open up their iMobsters game they can then enter that code into the last invite option in the My Mob menu, which is joining through invitation codes.