The Basic desktop edition is not available for prior year tax returns from the TurboTax website - https://turbotax.intuit.com/personal-taxes/past-years-products/
There may be a Basic edition for 2015 that you can purchase from an online retailer, such as Amazon.
Or you can use the free forms, schedules and instructions for a federal tax return from the IRS website - https://apps.irs.gov/app/picklist/list/priorFormPublication.html
