I can't feed my horse. What do I do?

I managed to get a horse to like me. That's swell. But I can't seem to figure out how to feed the horse. I right clicked on the horse and tamed it. No feeding was involved.

I have some wheat in my hand. Right click and I'm riding horse. Left click and I beat horse with wheat, leading to dismay and confusion on both our parts.

Tried the "mob effects" button but that doesn't let me feed the horse.

Tried searching, and all the results I get just tell me to give the horse wheat. That's not my problem. My problem is that when I try I end up smacking my horse in the face with wheat. The horse don't like it. He goes all red and runs away.

Exactly how (like what random key mapping on the pc) do I use to feed the horse? I am playing on PC, the Windows 10 version of Minecraft.

Horses will only eat when they are missing health.

Sugar - Heals 0.5

Hearts Wheat - Heals 1 Heart

Apples - Heals 1.5 Hearts

Golden Carrot - Heals 5 Hearts

Golden Apples - Heals 5 Hearts

Enchanted Golden Apple - Heals 5 Hearts

Hay Bale - Heals 10 Hearts

Source