Normally a applied I cord trim would be used around an arm hole. I'm not familiar with your pattern, but assuming the arm does not have active stitches (bottom up/top down knit with bound off stitches for arm hole shaping) starting at the underarm seam, (with the right side of work facing you) pick up one stitch, use knitted cast on and add three stitches, move all stitches back to left needle. Knit 2, knit 2 together, pick up new stitch, move stitches back to left needle (if using double points just switch hands without turning). Repeat around arm hole and finsh by grafting stitches.
Hint for making both arms the same: would normally use double points, one size smaller than the body needles. When picking up stitches on the horizontal, pick up one stitch for each stitch. My rule of thumb for picking up on diagonal or vertical is for every three rows, pick up two stitches.
Applied I-cord can be two to five stitches thick. Hope this helps.
