If you have NOT already filed your return for 2020, then you can go back into your return and add the additional information.
If you have already filed your return, then you will need to wait for the IRS to either accept or reject your return. If it is rejected, you can include the additional information before resubmitting it. If it is accepted, then you will need to file an amended return in order to include the additional income.
Take a look at the following TurboTax articles for more details and information:
Where do I add or enter a second W-2?
How to amend (change or correct) a return you've already filed