Been searching around the incredibly tedious revamped Delta.com* site for quite a while and cannot figure out how to pull up a reservation that isn't already listed under "MY TRIPS" and add the passenger's Skymiles number.

* So far, imo, they've wasted a hefty chunk of change on the overhauled site (for which they have remarkably further reducing its usability and left unaddressed most of more important existing limitations - not enough time here to get into all of the reasons why though).