Normally when there is a partner discount, there should be a special webpage accessed from the bank's website that takes you to a special TurboTax page. Then you use that page to start your return and go there each time to work on it and file. That's how it knows to apply the discount.
Usually a partner discount is "Up to" $20. That means it varies depending on which product edition you choose. The actual discount may be $10 or $15, for example, in lower editions.
Have you already paid? If not, you may be able to salvage the situation by following the steps in the last section of the FAQ below; i.e., signing out of all Intuit accounts, then deleting the Internet browser cache and cookies and going to the discount website linked from your bank, and signing into TurboTax there.
FAQ:
How do I get my TurboTax affiliate partner discount?
https://ttlc.intuit.com/replies/4652791
