How do I file a tax return for 2019 on an income of less than $5,000?

You are too late to use free software.  Online TurboTax is only for 2020 returns--no other year.  If you want to prepare a 2019 return for free you can use the paper forms to mail in:

2019

2019 Instructions

 https://www.irs.gov/pub/irs-prior/i1040gi--2019.pdf

1040  https://www.irs.gov/pub/irs-prior/f1040--2019.pdf

1040SR  https://www.irs.gov/pub/irs-prior/f1040s--2019.pdf

2019 Schedules 1-3

https://www.irs.gov/pub/irs-prior/f1040s1--2019.pdf

https://www.irs.gov/pub/irs-prior/f1040s2--2019.pdf

https://www.irs.gov/pub/irs-prior/f1040s3--2019.pdf

https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

if your income is only $5000 on a W-2 and there were no tax withholdings, there may be no requirement to file.... can you please state more about your situation?  W-2 or misc-1099 or other form?   living situation, etc? 

are you asking because of the stimulus?