Every taxable crypto transaction gets reported on Form 8949, which is the same form you'd use for stocks and other capital assets.
From there, the totals flow to Schedule D, where your short-term and long-term gains are combined and added to your tax return.
For each transaction you'll need the asset name, the date you acquired it, the date you sold or disposed of it, the proceeds, and your cost basis.
If you've had dozens or hundreds of transactions, crypto tax software like Koinly or CoinTracker can pull your history directly from exchanges and generate a ready-to-file Form 8949 automatically.
Failing to report crypto is one of the more common audit triggers right now, since the IRS has been cross-referencing exchange data through its John Doe summons program targeting major platforms like Coinbase and Kraken.