Since you do not maintain inventory:

1. When you get to the screen that asks "What kind of expenses did you have for <your business>?", choose the drop-down for "Less common expenses" and select "Other miscellaneous expenses"
2. Click "Continue"
3. Scroll down to Expenses; find "Other miscellaneous expenses"; click on the blue Start button
4. Enter a description such as "Merchandise purchased" and enter the cost of the merchandise that you purchased during the year, including any amounts paid when you purchased the business.