This treatment is suitable for a rounded neck. You create ribbing and attach it to the garment.
Cast on an even number of stitches, using a circular needle three sizes smaller than the needle you used for the body of the garment. Knit 1x1 ribbing the depth you wish for the collar. Using a backstitch, sew the live stitches of the collar to the neckline of the garment.
Consider using a contrasting yarn for the stitching. Work a deeper ribbing to create a turtleneck. Work the ribbing in a back-and-forth strip to create a stand-up collar for a scuba jacket.
