To change your site's theme, follow these steps:
- Tap on the "My Sites" tab in the lower left corner of your screen.
- Select the site.
- Tap on the "Themes" menu item.
You'll be shown all of your available themes for that site. You can also search them by name.
- Once you find the theme you want, tap on it.
- Tap the "Activate" button in the top right corner of the screen.