How do I share an existing album?
Solution 1:
You do have to create a new shared album, but you can create the album from the contents of the existing album so you don't need to find the images again manually.
- Open the album.
- Choose Select in the top right, then Select All in the top left.
- Tap Share in the bottom left, then create a new iCloud Photo Sharing album as usual.
Once you've created the shared album, you can delete the old album.