Add a NAS of type "Cisco IOS (RADIUS)" and you'll be abled to enter cisco-av-pairs.
You may need to enabled it first in interface config.
av-pair formats are documented on cisco.com if you look hard enough, typical examples are
"ip:addr = x.x.x.x"
"ip:inacl#1=foo"
"ip:inacl#2=bar"
etc
Note that they are NOT checked for syntax or semantics
