How to set a lock screen wallpaper on iPhone

1. Save the image to Photos. On the wallpaper page, tap Download wallpaper. When the image opens, tap Share and choose Save Image, or press and hold the image and tap Save to Photos.
2. Open it in Photos. Open the Photos app and tap the image you just saved.
3. Tap Share, then Use as Wallpaper. Tap the Share button (the square with an arrow) and scroll down to Use as Wallpaper.
4. Fit it and add it. Pinch to position the image, tap Add (top right), then choose Set as Wallpaper Pair for both screens, or Customize Home Screen to use something different there.
5. Optional: keep the clock clear. If the depth effect hides your clock, tap the three dots on the wallpaper editor and turn Depth Effect off.

Questions

What size should an iPhone wallpaper be?

Recent iPhones use screens around 1170×2532 to 1290×2796 pixels. A 1170×2532 image fits all of them; iOS scales it slightly on the larger Pro Max models.

Why is my wallpaper zoomed in?

iOS adds a small zoom for the parallax effect. In the wallpaper editor, pinch out to fit the whole image, or turn off Perspective Zoom where it's offered.

Can I use a different wallpaper on the home screen?

Yes. After adding the lock-screen wallpaper, choose Customize Home Screen and pick another photo, a color or a blurred version.