If you want to play 'Arranged team' ladder with someone you know, you need to click on the button
'Arranged Team' then invite people you want to the team and then start the search for a match on ladder. Your friends need to be in the same channel as you, so that you can see their names and invite them to be in the game lobby searching for a game. I can't believe im still wasting my time on a war3 related topic. Well that was for the last time.