Open the Settings app
Tap Wallpaper
Tap Add New Wallpaper or Choose a New Wallpaper
Select a wallpaper from Photos, People, Photo Shuffle, Emoji, Weather, or Astronomy
Adjust the image if needed
Tap Add
Choose Set as Wallpaper Pair, Set as Home Screen, or Set as Lock Screen
Confirm your selection
Or, press and hold the Lock Screen
Tap Customize or the plus button
Choose a new wallpaper
Tap Add and set it as desired