In order to view your Prior Years Tax return from Federal Free Edition you will need to upgrade to a "Plus" package or a higher version of TurboTax.
Keep in mind that merely selecting the upgrade will not allow you to benefit from it (view your prior years return). You will need to proceed to the Review Your Order page, select a payment method and pay for your upgrade before it is applied.
You can then go back to "My Tax Timeline" and view your Prior years returns.