You can check AC forum in this thread:
http://www.assettocorsa.net/forum/index.php?threads/protyres-v1-0-0-it%E2%80%99s-all-about-the-tyre.43361/

User B-RIDDICK at the AC forum supplies zip's for many cars, here you will find many setups for mod cars
https://drive.google.com/drive/folders/0B2P8YTKOyGSLR1J5OXBqU0RvMk0?usp=sharing

Extract the car folder into "\apps\python\proTyres\cars_mod", thats it!

proTyre will also read all open mod cars directly from the AC car folder

If you miss your favourite car, send an request in the AC forum or at racedepartment support tab
http://www.racedepartment.com/downloads/protyres.14030

To add an new mod car, extract tyres.ini, thermal and wear curves using QuickBMS,
if you need to ask how then maybe you should not do it ;)