Row 3 *(k2 tog) 3 times, (yo, k1) 6 times, (k2 tog) 3 times, rep from
A yo involves bringing your yarn between the needles to the front of your work before knitting the next stitch - it will create a new stitch which you will knit on the next row. You can, more than likely, expect to get a holey effect this way but that is probably part of the pattern so don't panic!
It won't create more stitches than you started off with because you have done k2tog - making two stitches into one.
The instructions I've quoted for the row you're having difficulties with show that you should k2tog 3 times, yo then k1 6 times then k2tog 3 times and this should be done all along the third row until you have no more stitches left to work.
Does that help at all?