There are tutorials online though that you can find and a lot of different directions on how to felt wool. I used stuffing as the center to use less felt as felt is expensive. I also found an entire bag of wool at Craft Bits and Pieces (a second hand arts and crafts store) for $3.00!!! Amazing deal!! I've created 9 medium to large felted balls and 5 small ones (I'm still in the process of making a necklace with the small ones) and I still have a bunch of felt left.
Anyway loved creating these felted wool balls. It's relaxing and creative. You can create whatever you want as far as colors and designs. I used hot water and soap when finished to tighten the wool up instead of keeping a fluffy look and to dry them I put them in the oven at 150 degrees and left them until I remembered to check them (about 45min.). I just put them in the oven to dry them faster because I'm impatient. You could put them on a towel and set them in a sunny spot and let them air dry. That would be the eco-friendly way.
My next step is going to be to had ribbons, yarn, beads, etc... into some of them. I'll post them when completed.