don't know how to open stitches...but would using a bit of velcro be easier?

No, I don't think you can open the stitches. But you could use the buttonhole stitch or a tigth zigzag stitch on your sewing machine to make a buttonhole, then cut it open.

You could also probably, using your finger, enlarge a spot where you want the button hole to be...then blanket stitch around it by hand, using your yarn to keep the hole there. The sewing machine bit would work too, but I wouldn't use the zigzag....just straight stitch, and 2 rows of that...then sip between the rows for the hole.....the machine stitching will prevent it from 'unknitting' itself!