you can do this from the cortex rcon screen or by using the in-game rcon. you will not see antying returned to you as you enter these commands, so it seems like they are not working, but if entered correctly it will work.
***if doing this in-game from the console, log into your rcon "rcon login 'pass'" then put "rcon exec" before the commands below***
pb_sv_httpAddr xx.xx.xx.xx //this is the ipaddress of your game server
pb_sv_httpport xx //this is the port you want to use, ex: 88 or 8888. just be sure its not already in use.
pb_sv_httpKey 'yourkey' //this is like a password so only those who know it can connect
pb_sv_writecfg //this command permanantly writes the changes to a file that will load every time your server starts
pb_sv_restart //this restarts the punkbuster engine, enableing the changes you just made.
now connect to http://xx.xx.xx.xx:xx //replace the xx's with your ip and port you setup above, such as http://100.100.100.100:88
now your admins can use the pb web tool