In Cloth Room, I create a [New Simulation…] (panel 1), give it a meaningful name and accept all other default values.
With the cloth selected, I click [Clothify…] (panel 2) to define the cloth object,
and I click [Collide Against…] to define the collision objects.
I use [Add/Remove…] and check Car and Ground, accept with [OK]
and continue with [OK] to accept all other default values. Now I [Calculate Simulation] (panel 4).
I see the cloth fall onto the car (the message tells that while calculating frame 8, the previous one took about 0.6 sec), and I can start to analyze this first result. Save your file.