Since no one has told you how....
- Create a dynasty with a coach.
- Once in the dynasty go to the coach info screen and create a new coach (RB on the xbox I think, but it tells you at the bottom of the screen)
- After creating this new coach, pick the team you want for him.
- You can do this for up to a total of 12 coaches/teams.
I don't know if you can use multiple real coaches in a dynasty.