Change album's main picture in Photos I have an iPhone 6s with iOS 10.  In the Photos app, there are Albums and each Album has a cover photo.  

How can I change the cover photo of an Album?
Tap the person in the People album.
Tap Select.
Tap Show Faces to focus on just the person’s face in each photo.
Tap the photo that you want to use.
Tap the Share Extension, then > Set Key Face.