I financed a new car this past year how do i enter that in the "major purchases"

[Coleen3]

The fact that you are financing is irrelevant. Enter the entire amount of the sales tax.

You can enter the sales tax you paid for the boat you purchased in 2017 by going to Federal>Deductions and Credits>Estimates and Other Taxes Paid> Sales Tax.  You will be asked if you paid sales tax on a major purchase, and you will be able to enter the sales tax you paid for your new vehicle. 

Sales tax is an itemized deduction.  If your state has a state income tax, you have to choose between using the deduction for your state tax paid OR the sales tax deduction, whichever is higher.  The TT process will suggest one or the other as you prepare your return.