In order to add bots to your Counter Strike 1.6 dedicated server you will have to do this :

1. Download here the podbot arhive and unzippe it.
2. Copy the podbot folder into HLDS\cstrike\addons - HLDS is the main directory of your server .
3. Open HLDS\cstrike\addons\metamod\plugins.ini and add this line under those who already are there :
win 32 addons\podbot\podbot_mm.dll

If you want to change bots number open HLDS\cstrike\addons\podbot\podbot.cfg and edit the lines:
pb_minbots 3
pb_maxbots 12