How do I make it so I can add more than one car on my resources? I tried archiving the files, but the cars wont appear in-game. I know this is possible to do as several people have made Automation car packs.
You mean Automation vehicles? Check this thread where I explained the same for another user: https://www.beamng.com/threads/getting-multiple-automation-car-to-work-in-1-mod.56842/#post-900718