Where do i go to put in car loan interest for the car in my business

You can enter the loan interest for a car used in your business under Other Common Business Expenses.

In TurboTax Self-Employed, enter the expenses on your Schedule C using these steps:

1. Click on the Business tab > Continue > I'll choose what to work on
2. On the Let’s gather your business info screen, in the Business Income and Expenses section, click the Start/Update button.  (See Screenshot #1, below.)
3. If you have already started adding information about your business, you will see the Here's the business info we have so far screen.  Click on the Edit box next to the business.  (Screenshot #2.)
4. If you haven't already started adding business information, continue through the screens to enter the needed information.
5. You will now be on the Your [business description] Business screen.  In the Business Expenses section, click on the Start/Update box next to Other Common Business Expenses. (Screenshot #3)  [Most business expenses will be added in this category.]
6. On the screen, Let's write off some business expenses, click on the Start/Update box next to Interest Payments.  (Screenshot #4)
7. On the next screen, Interest Payments, click on the Start box next to Credit Card, Loan and Other Interest.
8. Enter the interest paid on the next screen.