That's the easy part :)
Just post here in the forum stating that you're looking for an opponent.
Make sure you specify what you want to play.If you're looking for opponents for a particular scenario state the name of that scenario. If you don't know exactly what to pick,you might start by looking at the scenario stats found in our database:
If it's a QB specify the params.
There aren't any club rules regarding played scenarios/QBs but it's best to settle with your opponent what you'll be playing and how,before the game actually starts.
Assuming you found some willing victims,check your opponent's profile.
If he has won 30 games and lost only 2, you might want to play someone nearer your own skill level.
Don't lose hearth if your first games end up in defeat. Playing against a human opponent doesn't come even close to playing against the AI.