to start your rolled hem you need to cut the edge fo the fabric at a slight angle so that you can feed it through the foot then sew slowly and evenly. Another alternative I used to do when making wedding dresses, was to use a very narrow ziz zag stitch and just sew the edge of the fabric the zig zag causes the material to roll. Otherwise you can also use a narrow zig zag and encase lightweight fishing line, this gives a curled rolled hem and also adds a little weight to sheer fabrics. Some sergers also have a rolled hem foot which I think may be easier but I've never used it,