
In the server.cfg file, look for the following section if it already exists, or add it if it does not. See the related article at the bottom of this page for more info. Then you need to set a startup parameter on the server control panel to tell the game which file name to actually load. If you have an illegal copy, it is corrupted and will not install. Sounds like a bad install try reinstalling. This config file does not normally exist at start up, and you must create one manually if you want to change any setting beyond default (which include things like which missions to load). Make sure Call of Duty is run from the correct folder. We have a separate article in our Arma 3 Knowledgebase about how to create a server.cfg file for your Arma 3 server. Upload the mission files to the mpmissions folder in the main directory of your server.

To add missions to your Arma 3 server, first find the missions (or "scenarios") you want to use and download them to your local computer.
