Same way as a standard shirt collar. It has two layers, right? First sew down the outside layer, attaching it to the body of the garment. For non-jersay, I'd say stay stitch both pieces, first, as they are curved and may stretch, but jersey's always going to stretch - so do a practice run before messing up your final pieces. Then attach the inner part, possibly by hand stitching, with edges zigzagged, and turn the zz under as you hand stitch. The hand stitching is to avoid an outer visible sew line, but if you don't care about that, just sew it down with a line of stitches.

Just have to use stitches that work with the fabric, which is what the testing is for.