I am terrible at explaining things, but I'll try. When I knit 2 together normally, I insert the right hand needle in front, starting with the farthest left of the two stitches and continuing through the stitch on the right...knitting them together. When I knit two together through the back loop, I would start in back and insert my right hand needle starting through the right stitch & continuing through the left stitch & then knit them together. It's one of those things that sounds so much harder than it is. I wish I could explain it better.
The pattern looks beautiful, by the way!