You can install Omni-Bot from the "Addons" tab in Game Panel. (See the first image in the bottom)

To enable Omni-Bot, you need to set Enable Omni-Bot to on from the "Settings" tab in Game Panel and restart the server. (See the second image in the bottom)

To learn more about Omni-Bot, you can reference to this wiki page https://omnibot-enemy-territory.fandom.com/wiki/Gameet