No specific advice, but most importantly, don't get frustrated and do something you will regret. Don't be insulted by this advice, it is REALLY easy to rush it a tad and essentially ruin the frame. Be slow and walk away for the day if nothing is working.

Okay, here is some specific advice. We are more used to using threads on smaller diameter things like bolts. Large diameter threads are far more sensitive to angle of entry. I have had good luck by turning the cup the wrong way very slowly and carefully and gently until you can feel (like a safe picker) the end of the thread on the cup click over the end of the thread on the shell. When you feel this, gently reverse direction to the correct way and hopefully the threads will mate.

Patience grasshopper,

jim