Help Center

Scroll down on your horse's page to items and select the green plus, and then select Apollo's Lyre. It should take you to the customization page wherein you can select each letter in the name. Ensure you're selecting the letters outlined by a square box. From this you can make individual letters bold, underlined, italic or change their colour. (if you are on the mobile version, you may need to zoom in to make it easier to select the right option, as it is a bit small.) Once you're happy with your name design, click save.
You can also tap on the horse's image, and four icons should appear beneath it: animation, golden apple, Helios ray, and Apollo's lyre. Clicking the latter should also take you to the customization page.