If you have a "Nest Aware" or "Nest Aware Plus" subscription and your cameras are installed in the same Google Nest "home/structure" as your subscription, then your cameras should be part of your subscription automatically.
You can check on your Nest Aware subscription by going to Settings | Nest Aware in either the Google Home app or the Google Nest app, or by going to this Subscription Management page; if you select your subscription, the next page will display the Google Nest "home/structure" where the subscription is active:
I just wanted to jump in real fast to see if you saw MplsCustomer's reply and to see if you still needed some help on this or if you were able to get it sorted out. If you are still needing some help, just let us know and we'll be happy to continue helping.
I appreciate the help here, MplsCustomer.