I prefer to use yarn but you can use any type of think string you would like. First you need to separate your ornament balls by size. Count the balls starting with the largest ones first.
Cut your string about 2 foot long or shorter depending on the height of your ceiling. Cut as many string as you have balls all the same length For the large balls. Tie one end of the string to the balls and se to the side.
Repeat the process with the balls going from largest to smallest making your string shorter every time you go to a smaller ball.
After you have all the strings on the balls then you are ready to hang them.
You need to place all the larger balls all around the back and the sides of the tree. Use the other end of the string to staple them to the ceiling.
Make sure to place the balls in different areas because you want to have different sizes all over the place. I take a large ball then a medium then a small in a row and place them a few inches apart. I will make about 4 or 5 rows till it comes to the front of the tree. Then I will go in between all the bigger balls and place the small balls to give different sizes all over the ceiling and make your tree even more gorgeous then it was to begin with.