It is very easy to use Watercolor live wallpapers, just follow these instructions:
1. Select a background from the first screen. You can find them under "Select background" on the top of the screen.
2. You can also choose what elements to animate the screen by pressing the next circle next to "Select background".
3. Click "Apply"
4. Click "Set wallpaper"
5. You are done
Alternatively you can choose Watercolor live wallpapers from the phones "Live wallpaper" menu. Usually you can access it by long-pressing the current background in the home page of the phone.