Go into your chat that you wish to add someone to, click th…
Go into your chat that you wish to add someone to, click the (i) icon in the top-right area, click "See group members", then finally, click "Add" in the top-right area.
Go into your chat that you wish to add someone to, click the (i) icon in the top-right area, click "See group members", then finally, click "Add" in the top-right area.