1. Go to the "My Horses" page in your Howrse account.
2. Select the Horse you want to feed from the list of your Horses.
3. Click the "Actions" tab at the top of the Horse's page.
4. In the "Actions" tab, find the "Feed" button and click on it.
5. Select the "Apples" option from the list of available foods and click on it.
6. Your Horse will be fed the Apple and its energy level will increase.