If you have been selling products as a business, then you will enter your income and any associated expenses such as PayPal fees on a Schedule C.  You may or may not receive a Form such as a 1099K from Paypal, but either way you can enter your self-employed income/expenses for Schedule C by following the instructions below -

• Log into your account and click Take Me To My Return (you must click this before searching if you are not already in your account)
• Type “Schedule C" in the search box, top right of your screen, then click the magnifying glass
• Click the "jump to schedule c" link in the search results.
• You will arrive at the Your Business summary page where you can add a business (selling your art products)
• Follow the onscreen instructions to enter your business income and expenses