You become capable with the Medicine skill. If you are already capable, you become proficient. If you are already proficient, you gain expertise with it.
Additionally, you can mend wounds quickly and get your allies back in the fight. As an action, you can spend one use of a healer’s kit to tend to a creature and restore 1d6 + 4 health to it, plus additional health equal to the creature’s maximum number of Health Dice. The creature can’t regain health from this feat again until it finishes a short or long rest.