Paintstormstudio.com

I recently picked up Paintstorm Studio for my iPad. I use it with the Apple Pencil.
There's a couple of things I haven't worked out but the main thing is getting a picture from my camera roll to Paintstorm Studio.
Even copying and pasting layers is a problem for me.

Can someone please help me figure out how to do these?

Many thanks

If you want to combine several images at one document: Open it, select all (or area) of one image by selection tool, copy it from menu-edit-copy, swap document and paste it to your second document.