You can report your expenses from your activity as a business on Schedule C, self-employed income and expenses. You are technically considered to be running a business regardless of whether you actually made the mark to market election or not. Please see this link for additional guidance on how to enter your transactions within TurboTax.
For guidance on how to enter them in TurboTax, please see the steps provided by JohnW152 in this thread. If you are in the Desktop version of the software, you can click on forms on the top right to view Form 6781.
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