play friendly with a LAN user against AI enemies

[Victor]

Step 2)
Connect to the server, and say "/autoteam 0" in the console.
If you have other people there, they need to press F1 to vote yes.

Step 3)
Press and hold TAB to see client numbers of players (the number in the round brackets) who's on a certain team.
Type "/forceteam <cn> <team>" to call a vote to switch a player to a certain team. For example, if player (5) should be switched to team BLUE, type "/forceteam 5 1" (5 is the client number and 1 is team BLUE).