you need linux to install the freeradius.
basically its like this:
1. install redhat (during the configuration, it will ask if you want a GUI interface and the type of options you want, select SERVER and the option for GCC (its the compilar you will need to compile the freeradius code)
2. download freeradius
3. uncompress it
4. look at INSTALL file the in subdirectory it creates and follow the instructions in the INSTALL section of the document. Basically:
c. make install
5. once that is set, you can configure the files in /usr/local/etc/raddb to collect the files. You can get the specifics from reading the docs in the freeradius site.