Amy definitely has videos for this!!!
Well, she has videos for a knitside bar increase anyway.
But once you see the video, you'll get the explanantion for the purlside.
The video for the knit bar increase is on this page:
see: k1 f&b aka kfb
On the purlside of your work, you would do "purl the front of a stitch, then purl the back of the same stitch" (see Amy's abbreviations page).