Go to this TurboTax website to complete and e-file a federal extension request - http://turbotax.intuit.com/irs-tax-extensions/
NOTE - Filing for an extension gives you up to October 15, 2020 to file a federal tax return. It does not give you an extension for paying any taxes owed. Federal taxes owed have to paid on or before July 15, 2020 to avoid a failure to pay penalty and interest.
