Sew an elastic together to fit your childs waist.
Messure the tulle to the length you would like your tutu to be and double it.
Cut you tulle.
Fold it in half and simply knot it around the elastic
You can also put 2 pieces of tulle together and tie it as one !
I found all the supplies at the dollar store .... it cost me $8 to make it :)
You can even make a matching bow :)