Under what section of Turbotax do I enter my 2021 COVID-19 relief payments?

To clarify

are you referring to the individual Economic Impact Payments or some other business relief? 

To get to the stimulus questions in TurboTax at any time, you can search for stimulus or recovery rebate credit then hit ENTER and there should be a Jump to link

If you are trying to trigger it,

Click on Other Tax Situations at top

Click on Let's get started

Answer some questions then Continue

Then click on Let's keep going

Next screen is for the Third Stimulus, if you qualify

If you did not get prompted to enter your stimulus information, that means you either:

1. Filed as a dependent being claimed on another tax return, or 
2. have an AGI too high to claim the recovery rebate