Where do you see it needs to be mailed?  I would just attach a PDF.

A qualified distribution from a retirement plan for the birth or adoption of a child of up to $5,000 if made during the 1-year period beginning on the date your child was born or adopted. Attach a statement that provides the name, age, and TIN of the child or eligible adoptee.

https://www.irs.gov/instructions/i5329#en_US_2021_publink13330rd0e334

https://www.irs.gov/pub/irs-drop/n-20-68.pdf#page=13