You can claim expenses related to your professional activities as a dog walker: insurance, park permits, poop bags, leashes, transportation costs, online advertising, print advertising, website hosting, invoicing software, any other software or services used to support your business, etc...
Just make sure you have receipts for everything you're claiming.
In TurboTax we'll ask you at the beginning if you're self-employed (see attached screenshot).
If you've already started your return and want to get back to the Self-employed expenses section from the main navigation choose Income > Self-Employment and TurboTax will guide you through everything related to both your income and expenses.
