MUD stands for Manufacturer Usage Descriptions, a standard manufacturers can use to describe what sort of network access their devices need.
Each MUD file contains access control lists that use various classes. When you click on the checkboxes in MUD maker, additional information will appear below that you will need to fill out. Just choose which classes are appropriate for your devices. If you need more entries per class, hit the + button.
Once you've developed your MUD file, plop it on a server somewhere. Then have your device announce a URL pointing to that file. This can be done with LLDP, DHCP, or in a certificate.