I am a frequent traveler. Can I earn points on car bookings?

Yes, for car rental companies that have their own program, you will be prompted for your frequent renter number.

On the page where you enter your personal information before finalizing your booking, at the bottom after you are offered travel insurance, you will see this.  

When you enter your information, it will become a part of your booking and will be passed to the car rental company.

For car rental, you pay when you return your car.  If you purchase insurance, you will be billed immediately.