The round says,
*yo, p4(5,6), sp2po, p4 (5,6), yo pl,sm; rep from * to end
how do you yo when you're already purling?
A knit YO is the same as making a knit stitch except the R needle isn't inserted into a st on the L needle. A purl YO is the same - just wrap the yarn around the needle like you're purling it, start in front, go around to the back then to the front again between the needles.
Here is an article explaining yarn overs very well. LINK