Hi there,

You would need to authenticate first. You could use the following command:

doctl registry login

Or if you prefer not to use the doctl command, you could login with an API token which you could generate via your DigktaOcean control panel. And then use it as the username and password by using the following command:

docker login -u ZDRhYzzzz -p ZDRhYzzzz registry.digitalocean.com

For more information you could check out the following documentation:

https://www.digitalocean.com/docs/container-registry/how-to/use-registry-docker-kubernetes/#docker-integration

Hope that this helps.
Regards,
Bobby