How do I share a photo album in the iCloud

Sign in with Apple ID and account credentials at www.icloud.com , click on photos in album selection , select photos and take cursor on top menu bar file > share with desired options messages , air drop .....

Note : a single album or albums can't be selected and shared , however photos inside the album can be shared , the reason photos are already in system photo library System Photo Library overview for Photos on Mac - Apple Support

And iCloud photos are syncing Set up and use iCloud Photos - Apple Support

Change preferences in Photos on Mac - Apple Support

Send feedback Feedback - iCloud - Apple

See if anything here helps.

Photo Sharing - iCloud.     

Shared Albums aren't working.