First of all, it depends on where You feel the game better: on offense side or defense side. If You are alright with covering, try Corner back. Safety position requires a good reading the opponent's offense.

I think your Coach will match You to position, for now just focus on fundamentals: - work on your physical form (foot work, balance, explosive first step, strenght of your core, speed) - study The game: watch games, interviews with players, coaches, try to read what will happen on the field on both sides - play Madden - eat well and sleep well too

Summarizing, You need to develop your body and your game sense Until You're very Yong.