To register your bank info with IRS for the stimulus payment you have to provide your Adjusted Gross Income (AGI) from your 2019 return, as well as either the refund amount or the amount you owed on that return. If you haven't filed for 2019 (or you have and IRS hasn't processed it yet) you should enter those same amounts from your 2018 return. Remember AGI is a specific number from your tax return and not just your "gross income". The IRS uses that for security purposes to ensure you are the taxpayer in question and not a scammer.
