If you still have the needle in the last stitch you bound off take it out and pull slowly on the tail so that the stitch comes out. When you see a stitch loop put your needle in it from left to right. The proper way to have the stitch sitting on the needle is with the leg in the front a little ahead of the leg of the stitch loop behind the needle.
When you are back to where you have the 23 stitches knitted as you are supposed to, just set it up so that the needle with the 23 stitches you just made is in your left hand and the other needle in your right hand that you will knit with. Purl 2 stitches and lift to bind off, p1, lift to bind off, continue like that until you have bound off the 6. In other words bind off in purl stitches, since it is a purl row.