You're working with 3 needles (or 2 needles and a stitch holder). Put the working needle with the sleeve sts, right side facing you, yarn dangling off the needle tip, in your left hand, fold the hem up and away from you so that the wrong sides are together. Hold the cast on needle also with the left hand and use the 3rd needle in your right hand to knit the stitches, one from each needle. See if this
tutorial helps.