You can input your self-employment expenses in the self-employment section of the interview. To get there, click “Find” (the magnifying glass icon) in the top right. Type “self” in the search bar. Select Self-Employment from the list, then click “Go”. There you can create a new business or edit an existing one.
After filling in some basic info and your income amounts, you will get to several different sections where you can enter your expenses.