How to add a 2' cable to a cirular cardigan neckline

I have almost finished a cardigan in stockinette but bordered by a 2" cable on the bottm, cuffs and 2 front pieces. I have cast of for the neck but wish to finish it in the same cable. How? Knit it in or sew it on? Thank you for your help. Blueheron4

One easy way to do it is to put the sts for the front cable borders onto st holders when you get to the beginning of the neck shaping. The pattern may have you bind them off at this point but don’t. Finish the neck shaping and shoulder bind off, then join at the shoulders. Go back and put the front border cable sts back on needles and continure both cables until they are about long enough to meet at the back of the neck or at one of the shoulder seams. Baste them to the neck shaping and join by grafting or 3-needle bind off.