If you repaid it IN 2019, the repayment should be shown in box 4 on your Form SSA-1099 for 2019. The repayment is already subtracted from the net amount in box 5. Just enter the box 5 amount in TurboTax as it appears on the SSA-1099.
If you repaid it IN 2020, it will be handled on your 2020 tax return, even if it was a repayment of benefits that you received in 2019. You do not enter it in your 2019 tax return.