With right sides together (that is the pretty sides) align the main fabric and the band fabric and sew down the long edge using a 1/2 inch seam allowance (that means from the needle to the edge of the fabric it should be 1/2 there is probably a mark on your sewing machine).
Finish the raw edges with a serger or a zig zag stitch (when I teach kids I do this step for them).
Fold back the band. With right sides together match the short ends of the fabric together. Make sure your seam line is lined up. Pin in place or if you're confident you don't need to pin, beginners should pin though.
With a 1/2 inch seam allowance sew down the short edges to make one big tube.
Finish both edges with a serger or zig zag stitch (I do this step for the kids).
Iron the edge of the band side under wrong side together 1/2 inch and sew down with a 1/4 seam allowance (usually lining the fold of the fabric with the edge of your presser foot).
Iron the top edge of your skirt under wrong side together 1 inch. Sew down with a 3/4 inch seam allowance making sure to leave about a 1-2 inch hole to insert the elastic.
String your safety pin on to one end of your elastic. Thread it through your waist band. Make sure it did not get twisted along the way. (I usually have to finish this for the kids but they can start it and given enough time they can probably do the whole thing but it's a lot of work for little fingers)
Over lap the ends of your elastic one on top of each other about 1/2 inch and sew back and forth 3-4 times.
Sew the hole closed in your elastic band by sewing over where your stitches left off over the space of the while and where your stitches start again.