These Tsubasa Reservoir Chronicle mobile phone wallpapers are completely free to use. Simply transfer them to your phone via blue tooth, infrared, SD card, or attaching it to an email and sending it to your phone's email address.
Once it's on your phone just select it as you would any normal background image or photo. Done!
Note choosing "stretch" or "fill screen" may diminish image detail. The "centre" preference is recommended.
Have fun!