Yes you can. I had to do it when I got mine. I don't remember the process, but when you log into your skymiles account, it can be merged there. You might have an easier time just calling in and letting them deal with it, because I remember having issues.
I had the same thing and it was simple when calling in. Wasn't even aware there was a way to do it through the app. But the again I just have issues.
As a general PSA, I thought there is a field in the application where you enter your existing SkyMiles account number to use that, avoid getting assigned a new SkyMiles account?
This is what I used when I received my Delta AMEX. It flawlessly merged the two accounts.
ETA: I used my NEW number as the 'primary,' simply due to the fact that the number is listed on my physical AMEX card. Not sure if that matters either way, though.
I did this when I got my Reserve. I missed the part on the application where it asked for my SkyMiles so they gave me a new one. I just called Amex and they fixed it and sent me a new card.
