After completing a purchase your choice of Lock Screen Animations is sent to you by iMessage.
1. Save the images to your Photos library (long tap on the photo to get the option to save)
2. Open the photo in the Photos app
3. Open the sharing menu
4. Scroll along the actions (bottom row of icons) to find “Use as Wallpaper”
5. Tap the icon. Resize photo by pinching inwards (to show the whole image on screen).
6. Live Photo should be selected by default (near bottom of screen); if not tap to select it.
7. Tap “Set” (bottom right) > Tap “Set Lock Screen”
8. You’re all done. When your phone is on the Lock Screen 3D Touch your screen to animate it.