Instructions
Select the Medic as your soldier in the multiplayer campaign. In addition to being the only class that can heal teammates, the medic also can use a long-range rifle.
Restore the life of mortally wounded teammates using the Revive Gun. Approach the body of your downed teammate. Crouch next to him by pressing "L2" and press the "O" button to administer a shot that will revive him. After you have used the Revive Gun, it will take a couple of minutes to recharge.
Drop Med Packs for your teammates to pick up using the "R2" button. While playing the multiplayer game, you will be accruing experience points that eventually will level up your Medic character, gaining the ability to drop Med Packs. When your teammates pick up these packs, they will spring back to life after being mortally wounded. Once you become a level 2 Medic, you will start out the campaign with one of these packs. To obtain more, search the game map for them. You can hold up to three at once.