inside edge

my King Cole pattern for a pull over baby sweater that has a 3 button placate and hood says the following: with right size facing and commencing at inside edge of 5 cast off sts, cast on 1 stitch, pick up and knit 12 stitches. I am at the point that I am creating ribbing up the right side of the neck placket and around hood. HELP and I am an experienced knitter

Welcome to KH!
What is the name or number of the King Cole pattern?

It looks like you’re going to start with one stitch cast on the right needle and then proceed up the edge of the placket to the neck picking up 12sts.