If you have already downloaded the file, here is the general process for installing it (using ETS2 as an example): Extract the .rar file using WinRAR or 7-Zip. Step 2: Look for a .scs or .zip file inside.
This specific archive typically contains custom "paint jobs" or "skins" for in-game vehicles. Based on the filename (which translates from Hungarian to "Cars Paintjobs"), it is often found in modding communities for: autok paintjobok.rar
Always run files through VirusTotal before extracting them. Mod files can sometimes contain malicious scripts. If you have already downloaded the file, here