Hello everyone!

I wasn't sure where to put this, I hope this is the right place.

I booked what I thought was a roundtrip Delta flight to Japan (I fly out in late March,) and I decided right after to join Delta Skymiles.

I THEN realized that I was flying a codeshare flight, and I was actually flying Korean Air out, and Northwest in. I want to get miles for the flight, so do I try and claim it through Delta? And how do I get miles on a flight I booked before I joined?

Thanks a lot!