Authorization Computers using MAC address

Hello everyone, So I have already setup the Freeradius server, authenticate WIFI users using username and password. All working smoothly so far. Our office also have about 5 desktop computers, sharing the same EdgesSwitch How could I go about authorizing only our office computers using its MAC addresses? This is to prevent outside guests/visitors plug our LAN cables to their laptops I see in the "radcheck", there is "attribute" for user/password is "Cleartext-Password" when using username/password. Can I change this to something that accommodate MAC address? Or I have to come up with a complete new setup? Thank you very much for your helps Kind regards James