Defeat the teams in classic challenge mode to unlock them in single player mode.
Getting Players In Dynasty Mode
Use the following trick to get any player and create a player with as high a rating as you want in dynasty mode. First, at the main menu, go to "General Manger", and trade, sign, or create whomever you want. Next go to "Season", and on to "Dynasty". Turn off the salary cap and alter your depth chart. You should now have all of your favorite players without having to pay too much for them.
Unlock Stadiums
To unlock the following stadiums, enter the required phrase as your user name.