It is not your "2020" tax return-- it is your 2019 tax return.
The forms to request an extension do not usually become available until sometime in March. Why do you need to request an extension so early? You can go on the IRS site and get the paper form to mail in later.
An extension request for your 2019 tax return has to be completed and mailed to the IRS using Form 4868 - https://www.irs.gov/pub/irs-pdf/f4868.pdf
The request gives you a six month extension to file the 2019 tax return on or before October 15, 2020. It does NOT give you an extension to pay any taxes owed. Any federal taxes owed have to be paid on or before April, 15, 2020 to avoid failure to pay penalties.
If you expect to have a balance due, you can also make a payment of your expected balance due by using IRS Direct Pay which will simultaneously request the extension. This will make it unnecessary to actually mail Form 4868.
https://www.irs.gov/payments/direct-pay
If you need to also request a filing extension for your state taxes, you would do that separately with your state.
https://www.irs.gov/forms-pubs/extension-of-time-to-file-your-tax-return
kind of early since returns aren't due until 4/15/2020