Measure your child's waist...or your waist (I think I'm gonna make one of these for me). You can leave the ribbon single or you can double it like I did. It just gives it more strength and sturdiness. Back to doubling...take that measurement and double it. Pull the loops through until it's in the middle of your ribbon.
Sew it in place. Burn (or singe) the ends of the ribbon so it won't fray if you wash it. I then sewed down both sides of the belt and over the end. For the end, I folded both sides inward, facing each other. You can just fold both ends over together if you want. And then you're done.