It's simple!
Step 1:
Invite your future squadmate to your new squad by just right-clicking on his or her login in chat or in combat. Also you can use "Looking for squad" channel (Optional). Your squadmate must approve your invitation.
Step 2:
Whenever you or your teammates attacks or been attacked - all members of the squad that were not in combat or were not on their way during their adventures will get into battle by your side.
