IRS Flagged my amended return

I filed an amended return which not have any monetary impact. The state accepted my return however the IRS flagged it. The IRS has requested I print the e-filed return and mail it to them. I am not clear exactly how to do this. Do I simply put the return in an envelope and mail it? Do I need to add a wet signature? Do I need to include any forms?

 

I’ve been searching for hours and haven’t found a clue what I need to do to satisfy them. Any help would be tremendously appreciated.