To access your current or prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/
The Form 4868 extension request will be included in the PDF download when you request all worksheets. To view/print/download any forms in the tax return you will have to pay the TurboTax account fees, if any.
Click on Tax Tools on the left side of the online program screen. Then click on Print Center. Then click on Print, save or preview this year's return. Choose the option Include government and TurboTax worksheets