Change Album Cover Photo
Set the album Key Photo so it becomes the album cover image.
- Open the album whose cover you want to change.
- Open the photo you want as the cover in the Viewer.
- Tap the on the bottom toolbar.
- Tap Extras > Make Key Photo.
Changing the still frame of a Live Photo is a different action. In the Viewer, tap the Live Photo badge, then choose Change Key Photo. See Change Live Photo Key Photo.