[Damon Williams]

You probably only have the base game of Assetto Corsa, which comes with a selection of cars and tracks. But Kunos (the developer of the game) also released paid "updates" called DLC's with new cars and tracks. Assuming you have the steam version of Assetto Corsa, you can buy additional dlc's from the steam store. During steam sales, those dlc's are actually really cheap.
Here's the steam page for AC:
https://store.steampowered.com/app/24421...tto_Corsa/

Actually, the ultimate edition is currently 90% off, which includes the game + all other content. That's a really good deal! Only $9 for everything! If you want to buy the dlc's separately, those are also 80% off right now.
Hopefully that explains a few things for you

Alexander you are exactly right. I realized those cars were from DLC packs I would need to purchase. Great timing  because Steam is having a crazy sale 90% off just as you mentioned. I purchased all of the DLC packs  so now that I understand the process and able to register I'm ready to jump in !.. Thanks for your explanation. It is very much appreciated