|Here's a link to my blog post, complete with photos, on inserting an invisible zipper when creating a fully lined dress.
Overview: Sew lining to dress only at neck and armholes. Set zipper teeth on seam allowance of one side of dress fabric (right sides together) as normal. Baste. Flip corresponding lining fabric over dress fabric and zipper. Stitch along baste line. Repeat on other side. To finish dress, sew side seams, center back seam, and hem.