Shorten existing sweater

How can I shorten a sweater that is too long? Need to know how to get it to the right length and then how to finish it off by knitting in the reverse direction from the original.

You can’t just take out the cast-on edge easily. I probably would use this technique to secure the stitches at about the point you want the sweater to be. Then you can cut the cast-on edge and unravel to where your needle iis, knit to where you want it and bind off.

THIS might help too.