Sorry it's too,late to start a 2020 online return or use the mobile app, either on Turbo Tax or the IRS.
To do a prior year return you have to buy the Desktop program here,
https://turbotax.intuit.com/personal-taxes/past-years-products/
You will need a full Windows or Mac to install it on.
If you have a simple return and want to file for free you can fill out the forms by hand.
