A Form 8308, Report of a Sale or Exchange of Certain Partnership Interests, is not included in the TurboTax personal editions.
The Form 8308 is only included in the TurboTax Business Edition. The Business Edtion can only be installed on a Windows based personal computer, not on a Mac or online. The Business Edition cannot be used to complete a personal tax return, Form 1040.
Go to this website for the Business Edition - https://turbotax.intuit.com/small-business-taxes/