I've had sequin trims for years and never used them since I was not sure how to. Well, I finally decided to just wing and and found that they are really easy to work with.
Place the sequins down on the skirt and make sure that they are lapped going away from the presser foot, so the presser foot does not catch them while sewing. Sew, as normal, in the very middle of the trim and you are done. Easy!