private relay Apple ID account?

iCloud Private Relay is a feature that can be enabled when subscribed to iCloud+.

If you’re paying for iCloud, you have access to Private Relay.

Set up iCloud Private Relay on all your devices - Apple Support

PS: iCloud Private Relay isn’t available everywhere; in all countries and regions.

PPS: If you meant iCloud Hide My Email and not Private Relay, here is how that works:

Create and manage Hide My Email addresses in Settings on iPhone - Apple Support