I'm working on the body section of the Anker sweater and got stuck at the part where it says to "cast on five new stitches at the underarm using a spare cable or length of yarn." I'm not sure how exactly to do that or where the five stitches are supposed to go. Do I cast them directly onto the needle holding the body stitches, or do they go on a separate yarn piece first? A little guidance would be awesome.