Import Supporting Document for Form 5329?

I use the desktop TurboTax.
This year I need to file Form 5329 (didn't take IRA RMD on time, and need to request waiver of penalty).
The Form 5329 requires attachment of a Statement of Explanation.  I have created that letter in PDF format.  But how do I attach it (or insert it) to the Form 5329 in TurboTax?