Tame the horse first by mounting it until hearts appear
Hold a food item the horse can eat
Right-click or tap the horse with the food
Use wheat to restore a small amount of health
Use sugar to restore a small amount of health
Use apples to restore a moderate amount of health
Use golden apples to restore more health and help with breeding
Use enchanted golden apples if available for the strongest effect
Use hay bales to restore a large amount of health
Use golden carrots to help breed horses
Use the food again if the horse needs more healing or breeding support