Each license can be used on a certain number of systems - the cheapest will is only valid for a single machine, while more expensive licenses can be used on 10 or even an unlimited number of hosts. Cloudmin keeps track of the number of managed systems using each licence, and will allocate only those that have free systems remaining.
If you no longer want Cloudmin to use a licence, select the checkbox next to its serial number in the list, and click the Remove Selected Licences button. This will not remove the license from any existing systems, prevent it from being re-used in future, or perform any refunds.
To add a new licenses, you must first purchase it at the Virtualmin website, virtualmin.com. Once you have the serial number and key, enter them into the form on the second tab and click the Add Licence button.
To add several licences, find their serial numbers and keys and enter them in the text box in the third tab. Each license should be on a separate line, with the serial number and key separated by a space. When the Add Licenses button is clicked, each one entered will be validated and added to the list. They can then be used to create new systems with Virtualmin.
If you are purchasing a large number of licenses at virtualmin.com, you can configure Cloudmin to automatically find and fetch them for use on managed Virtualmin systems. This can be done on fourth tab - automatic checking will be done once per hour.