From an admin session on the server, open the Printers folder and access the Printing Preferences for the installed product. The license code can be entered into the Licensing tab. This applies to Server Edition only. Information on entering the code for the standard workstation version can be found here. To add licenses to an existing license, enter the license code and the new licenses will be added to the existing set.
Once the code is entered, licenses are allocated on a first-come, first-served basis when users first use the product. It is not possible to manually assign licenses to specific users. Licenses can be reclaimed by deleting the user from the Users list in the Licensing tab.