You don’t need any special setup, RFID readers will usually just show up as a keyboard on Windows. If you open Notepad, then scan the RFID fob, it should show a number come up.
So in SambaPOS, all you need to do is go to Manage, Users > User List, then edit the required user, put the cursor into the PIN field then tap the required fob on the RFID card reader. That will set the PIN as the ID of the fob.
To login to SambaPOS, just tap the fob on the RFID card reader on the login screen.