I am getting a message that time machine is full and will start to delete old backups. What do I do?

Well you could let it start deleting the old backups to make room.

Or you can get a larger external drive and move your Time Machine backups to it.

see > https://support.apple.com/en-us/HT202380

Hi rosegarden1939,

You have two choices:

1. Since your drive is full, you could let it delete the oldest backups you have, so there is room for new backups and it will continue working.
2. Buy a new, larger Time Machine drive, so you have space for lots more backups.

If you proceed with option #2, a good choice is the OWC Mercury Elite Pro: https://eshop.macsales.com/item/OWC/ME3NH7T04/. Just buy it with at least 3 times the storage space as your internal drive.

Cheers,

Jack