The second stimulus check is based on your 2019 information. If you choose to have your 2019 refund by direct deposit then the second stimulus money will be direct deposited into your bank account.
If you don't have a bank account on your 2019 return, then the IRS will mail you a check.
On your 2020 return, you will be asked about the stimulus money.
After the Other Tax Situations section of the 2020 TurboTax program you will be asked about the stimulus payment received or not received in 2020.
After you asked about the stimulus payment & you qualify, you will get the Recovery Rebate Credit (stimulus) on the 2020 federal tax return, Form 1040 Line 30.