Equip a Support/Medic class or a loadout with healing gear
Select the medkit, syringe, or healing gadget
Aim at the injured teammate if the game requires direct use
Throw or place the medkit near the teammate if it is an area heal
Use the revive/heal interaction when prompted
Stay close enough for healing range to work
Replenish health with ammo/health crates if your loadout provides them
Use healing abilities or gadgets on cooldown when available