hello my name is Gilberto Uriostegui, I'm new at this and am doing an internship in my teacher networks

I have version 2.1.10. tar.gz freeradius
I installed Ubuntu 9.10

freeradius first and unzipped and put into execution and let me open the port 1812, now I got into the user file to declare some users and declare some removing the # for comments that were no longer up there all very well. .

but my question is:

How I can add mac address on file?

or

 Do get in some other file?