This app is made to be simple and easy to operate. You don't need any special settings on your phone, as root for example. Your phone just need to be able to show Live Wallpapers. You can move and resize the image any way you like before setting it as a wallpaper.
Tip: cinemagraphs are specially beautiful for setting as Live Wallpaper. Search for "cinemagraph filetype:gif" at Google Images, for example.