To add bots:

1. Click Lobby Browser from the main menu
2. Click Create Lobby at the bottom of the following screen
3. Select the map that they want to play on from the Create Custom Game screen (either Predator or Mountainside)
4. Click Create Lobby after selecting the map
5. On the match setup screen there should be an Add Bot button, clicking on that will add AI to that player slot
6. Once all the setup is done, click Ready and the game should start