Check in the first post of this thread the schedule and choose a tournament that is not already taken. At the moment, the first one available for you to take is Indian Wells. Post your choice here and mmarto will write you down as the manager for that tournament.
You should open the tournament thread on weekend before the tournament start. If you play the game, you basically know what you're supposed to do then, but if you have some doubts, freely ask here.
He could also do Zagreb / Johannesburg / Santiago because Storm Lee is banned I see. But I don't know how long.