You will have to complete, print and mail the IRS Form 4868 for an extension on or before June 15,2021,

Note that the extension is only for filing a tax return, any taxes owed have to be paid by 06/15/2021 to avoid a failure to pay penalty.

https://www.irs.gov/forms-pubs/extension-of-time-to-file-your-tax-return

Victims in FEMA Disaster Areas: Mail Your Request for an Extension of Time to File

To request an extension to file your federal taxes after May 17, 2021, print and mail Form 4868, Application for Automatic Extension of Time To File U.S. Individual Income Tax Return.  We can’t process extension requests filed electronically after May 17, 2021.

Find out where to mail your form.

If you are a resident, your filing date has automatically changed to Jun 15,

There's nothing you have to do.

If you are not a resident, there's nothing you can do.