Login to the Kinetic Panel.
Stop the server.
Go to the File Manager.
Navgaite to .local > share > American%20Truck%20Simulator > server_config.sii.
Change the desired Settings.
Save
Start the server.
American Truck Simulator guide
How to configure your American Truck Simulator Server
This guide will cover how to configure your server from Max players, Vehicles, AI, Traffic, and Damage and many other options to customise your Server.