In the Photos app
You can change a memory’s music by choosing from memory soundtracks or Apple Music’s suggested songs. Apple Music subscribers can also access their Apple Music library and view suggested songs based on musical preferences or the content of the memory.
Play a memory, then tap the screen.
Tap , then tap , then tap Manage Photos.
Tap Select All to add all of the available photos, or tap photos without a checkmark to add individual photos. Tap photos with a checkmark to remove them from the memory.
Tap Done.
On the For You screen, tap Share photos and videos on iPad