Managing Cloud Storage

Removing an album is easy. In the desktop app, right-click and select "Delete Album". In the Mobile app, tap on the tri-dot icon for the album and in the resulting menu tap on "Delete".

Note, however, those actions only remove the album....not the images that are in the album. If your question therefore was about how to remove images from the cloud, you need to select them all and then select the delete option.

Note also, because Lightroom is a non-destructive editor any work that you did on those images will be lost when you remove them from the cloud.....so make sure you have preserved that work by exporting a copy of them first.