The bracelet that comes with Ivy is one size fits all and all you need to do to set it up is to clip the straps to Ivy by pressing down on the clips located on these separate straps and attach them to the metal part of Ivy.
Then, loop the bracelet and fasten it at the appropriate hole on your strap, and simply cut off any excess if necessary to make the perfect fit. Make sure Ivy fits snugly on your wrist but not too tight that it will cause any discomfort during the day or during your sleep.