OK Anders - I've looked into your skin, but there's a *.veh (vehicle) file included.
We aren't using veh files with the rf Caterhams, because that makes it a standalone car. If we go down that road, then we'd have to keep the server up to date with all the user created cars, but if we just use skins we don't need to touch the server at all. Right now, if you put your car into your install as a standalone car, you won't be able to connect to the server, because your car isn't present on it.
And more importantly, if I do update the server with your car, someone else who doesn't have your car will be prevented from joining the server.
If you just put your skin in the skins folder, it doesn't matter if you or anyone else has the skin present, if they don't have it, they'll see a default skin, if they do have it, they'll see your skin, but no-one gets prevented from joining.
Because of that, I'd urge you to only use it as a skin, not a car. I don't really want to update the server and possibly prevent people from joining while the Cats are still a new thing on RD. If it takes off, then we can think about a proper car pack, but for now, we'll just use skins, not cars. I hope you understand.
And for everyone else, that means just dropping the ATM_59_Academy.dds file from your archive into the rFactor\GameData\Vehicles\Caterham\Academy\Skins folder. If they do that, they will see your car, but no-one gets a possible refusal to join.