How do I file an extension for 2020 tax return. For a refund. No money owed?

It's way too late to get an extension for 2020, but you don't need an extension for a refund. However, to get a refund for 2020 you must file your 2020 tax return by May 17. You cannot get a refund for 2020 after that date. See the following IRS news release for more information.

Time running out to claim $1 billion in refunds for tax year 2020, taxpayers face May 17 deadline

It's too late to file an extension for 2020 but you can purchase the software and complete the return.  Purchase link is here.