Can I add car payments as a major purchase? It's financed through a dealership, and I don't know how to add it to my major purchases part of the deductions & credits.

If you are trying to deduct the sales taxes paid on a vehicle purchase, you would enter the cost of the vehicle and the sales tax paid in the year of purchase only.

If you are renting the vehicle, you would enter the lease payments for the year as the cost and the sales taxes paid during the year.