How can I heal with arrows?

According to the Wiki, Arrows of Healing give the same amount of health as their potion counterparts, but the healing effect can be cancelled out by the damage inflicted by the arrow. But, it is possible to gain a slight amount of health, as long as you shoot an arrow weakly and are wearing good armor, as potion effects go through armor of all types.

Arrows of Healing aren't really for players, but should be used on hostile mobs that take damage due to the Instant Healing effect.

But if you really want to get some hearts, then use Healing II.

In Bedrock though, low-range shooting of yourself results in 0.5 hearts, Healing or not.