What is the version of the following sentence with correct punctuation?

Collar Knit the collar back and forth on the needles from the left shoulder seam pick up sts so that there are 6 cm of overlap on the left shoulder 3 cm at each side of the shoulder seam
Collar: Knit the collar back and forth on the needles from the left shoulder seam - pick up sts so that there are 6 cm of overlap on the left shoulder 3 cm at each side of the shoulder seam).