Instructions
Walk up to Clover while not in battle and press the "Action" button to talk to her.
Select the option to trade items with Clover from her dialogue menu. This will bring up a screen showing both your inventory and Clover's inventory.
Move healing items like Stimpacks and Buffout to Clover's inventory. With healing items in her inventory, Clover will automatically heal whenever her health points go too low.
Defeat all of the enemies surrounding your party while in combat to heal Clover automatically. As soon as there are no longer enemies on your Pip-Boy's radar, Clover will be automatically healed by the game without needing healing items. The same will happen if you successfully escape from your foes.
Sleep in any bed to automatically heal both yourself and Clover.