The purl stitch is pretty much the same as always when working in stranded knitting or Fair Isle, but when you're on the wrong side of the work you can really see what is happening with the strands or floats that you made on the previous row (and that you will make on this row as well).
As on the knit side, change colors as required by your chart (remembering that you're working from left to right on this row) and again pick up the new yarn from underneath the old yarn in order to keep the piece from having holes.
You can see in the picture how the beige yarn is wrapped around the red yarn before the stitch is formed. That's the way it should be.
