I was told the same thing when I first got my chameleon.
If you already have the fiber, return it. You can easily keep up the humidity by buying a small plant like pothos or ficus, or even an umbrella plant. it will be MUCH easier to keep up humidity with a live plant.
Coco fiber can trap bacteria, give mold a place to form, and get damp and gross. It also gives crickets/worms a place to hide.
Throw out coco fiber and get a live plant

Much better