it is covered in the documentation, but here is brief list of steps:
Create a policy and service under user access to assign resources
create user, add mac address as account id, set MAC address as the type of authentication and associate user to service
Set access ports on switch for mac auth, radius pointing to imc.
One user can have multiple mac addresses or you can create one per one.
You can automatically create an account under mute termanal user, that will use the first portion of the mac, say add all HP or other vendor, so any device plugged in gets an account automatically