Hi Knitqueen! Thanks for your reply!
It looks like it's at the beginning and end of each row, here's the directions (and they give the increased by two/row stitch count):
Inc1 st at each end of row and following alt row (13 sts - which is increased by 4 over 2 rows)
I guess I just really am guessing at how to do a purl through the back loop part - I know I'll be coming from behind the left needle, and then do I come f/below the st on the left needle w/the right needle, looping and pulling through? It just seems so awkward.
I wish I could see a video of this.