I saw an offer for free QuickBooks Self Employed for one year if I file using TurboTax Self Employed. Is this offer still valid? If yes, how do I access it?

[Opus 17]

Quickbooks Self-Employed is an online only product that can only be used for one business, and its a monthly subscription.  If you have more than one business, you will need standard Quickbooks installed on your own computer.

The offer I know of is this one; a subscription to QBSE plus Turbotax. https://quickbooks.intuit.com/self-employed/

The offer you mention appears to be available as well, look under "more info" on the page for Turbotax SE.  https://turbotax.intuit.com/personal-taxes/compare/online/

Be sure to check the terms to make sure you agree with them.