Position battles are played during the weeks of your college career. Depending on the college that you enrolled in, you will need to battle other players on your team that are above you on the depth chart (1st String, 2nd String). These battles are put in replace of the practice sessions during your game week, and can be played every other week until you reach the starter position.
The battles are similar to practice sessions where you will need to accumulate enough points in order to win the battle. It's okay if you don't win a battle since there will be more in the upcoming weeks.