This is what the original skirt looked like.

Pin the skirt to create a silhouette you want.

Gather small bits and pieces of tulle together (or rip a piece out of a larger piece) and pin it onto the skirt.

Sew the tulle onto the skirt, and add more tulle.

Keep on adding more tulle- make sure that the volume is right, and add more tulle on areas that lack volume.

This is what the finished skirt looks like :D