At the time we prepared our software we had no idea that a stimulus check would even exist.  You can use these links to assist you:

These links may help explain and guide you through the process.

https://turbotax.intuit.com/stimulus-check/ link to stimulus registration (SR).  It is very important that you uses this link that says register now if you don't need to file taxes this year.  Otherwise, you will not be able to E-file a zero return. It also has the calculator.

The IRS says it is working on developing a web-based system for people to give the government their direct-deposit information. Keep checking www.irs.gov/coronavirus for more details on this.

Edited  04/07/2020

It may not have actually been sent.  Did you get a confirmation e-mail saying the IRS had accepted it?  If not, go to the IRS portal and register there ("Non-filers: Enter Payment Info Here").  If they say you have already e-filed, then use the other IRS link ("Get My Payment") , and enter your bank account information there.

I read two descriptions elsewhere about people who had prepared 0 income returns to mail in with TurboTax, and later they logged in to TurboTax todo stimulus registration.  The system just said they just sent the info to the IRS, without prompting about payment options (account numbers, etc.)  It turns out, in those cases the registration was never sent.  Those people were able to register at the IRS's portal.