The darts go on the sides of the squares, not on the corners. The easiest way is to quilt your square, then center the bowl that you are going to use with (right side of fabric up) it & just pin the excess fabric. Don't make it tight to the bowl, let there be a bit of ease. YOu should be able to gauge the width & depth of the dart. Then just fold the fabric, match the corners of the square & sew on your pinned darts. If you are still not sure, use a really long stitch so you can remove it if you need to adjust. Then turn it right side out & check it with the bowl for fit.