So if you want to do it, it’s a bit convoluted, but here’s what you do to learn how to add mods to City Car Driving:

1. Hop over to ...
2. Choose the car brand you want from the “All Brands” drop-down menu on the right side of the screen.
3. Click the car you want, then hit the blue “Download” button to save it.
4. Find the City Car Driving folder on your PC.
5. Drag the folders in the downloaded file and replace the ones in your original City Car Driving folder.