You'll enter both your business income and your business expenses (to include vehicle expenses) by clicking on the Business tab, then Business Income & Expenses, then I'll Choose What I Work On, and you'll be on the page entitled Let's Gather Your Business Info. Select the first section in the list, Business Income and Expenses (Schedule C, Form 1099-MISC) and click on Profit or Loss From Business. Follow the prompts as TurboTax will ask you about your business.
Once you've answered the questions, you'll be taken to a page entitled Your Business. You'll see sections on Business Income, where you'll enter what you earned, and Business Expenses where you'll see the category Business Vehicle Expense. Follow the prompts in that category and TurboTax will ask about your vehicle and allow you to input your expenses.
