From the Home screen prompt, tap WALLPAPERS (located on the bottom) then select one of the following:
Home and lock screen
Tap one of the wallpaper options displayed at the bottom then tap SET WALLPAPER.
If necessary, swipe the screen left/right to display more wallpaper options.
To view more wallpaper options other than those displayed:
Tap More images (may require swiping screen right) then tap one of the following (Gallery, Photos, etc.).
Tap the desired picture.
If prompted, crop the picture then tap Done (located in the upper right).