Perhaps you didn't installed it correctly. See this thread:
http://forums.bots-united.com/showthread.php?t=761
"podbotmenu" is a command for client only, dedicated server is not a client.
List of available commands for dedicated server:
ivp "addbot 100 2 4 ImABot" (add a bot named ImABot to CT team with skill 100 and GIGN skin)
ivp "killbots" (kills all bots in current round)
ivp "removebots" (remove all bots from the game)
ivp "fillserver" (fills server with auto assigned bots)
ivp "newmap mapname" (change the map)
ivp "weaponmode 1-7" (force the bot to use some type of weapon only)
Descriptions for each value of weaponmode:
1 - Knives only
2 - Pistols only
3 - Shotguns only
4 - Machine Guns only
5 - Rifles only
6 - Sniper Weapons only
7 - All Weapons (Standard)