For Essentials, there shouldn't be a limit at all. You should be able to add users directly, out of the box. Just tell your new user to login using the same Salesforce team Org.

For the managed package version, you would need to send us the Org ID and we can add more licenses. However, if you're just trying to trial Copado and we can't just outright add licenses, without going through a formal process with a SE & AE first.