Sorry it took me so long to get back to you. To answer your questions:
Donna Mae, you are correct. You use the dry cake mix right out of the box, sprinkled on the pineapple and first layer of peaches.
The peaches are NOT thawed. Use them frozen right out of the bag.
I believe the liquid from the pineapple and the juice that comes out of the frozen peaches as they bake is what supplied the moisture for the cake to bake up.
The melted butter is poured over the top of the whole thing.
Be sure to just put ingredients in the pan in the order in which they are listed.