You will first need to create the new media type for the printer in the Pricing Tab if it does not exist. More info on how this is done can be found on our Adding, Changing and Deleting Media article.
Next, double-click on the Printer group you want to add the additional media type to in the Printers section of Argos Manager.
Next, click the additional media button and check the media type you want to add in the small window that opens up and click on OK.
The changes wont take effect immediately, so if you're looking to roll this out immediately you'll need to restart the Argos Communication Service on the server.
When the user goes to bill their print jobs moving forward, they will need to change the media type using a dropdown underneath the printer name in the Argos Desktop Client.