It's called form 8453, see link
<a rel="nofollow" target="_blank" href="
https://www.irs.gov/uac/about-form-8453">https://www.irs.gov/uac/about-form-8453</a>
There are 8-10 specific types of paper documentation that the IRS allows to be mailed after e-filing, using the 8453 cover letter so that the documents you mail in can be associated with your e-file. (Other kinds of documents that can't be attached will require that you mail your whole return. But 8332 is one that you can use the cover letter for.)
You can download and print out a copy from the IRS web site, but I'm pretty sure turbotax will print one out for you if you follow the instructions.
