Register first, then manually add a subscription.
subscription-manager register
List all available subscription.
subscription-manager list --available --all
Attach a specific subscription.
subscription-manager attach --pool=XXXXXXXXXXXXXX
Verify that you now have access to subscribed rpm repos.
yum repolist
Check subscriptions
subscription-manager list
Unregistering a system
subscription-manager remove --all
subscription-manager unregister
subscription-manager clean