Clear a spot to work and make sure that there is a small towel covering the table top so that you can see anything that may drop or pop out during the process of changing the buckle.
Work with the back of the buckle towards you. Find the point where one side of the band is attached to the buckle, use a magnifying glass if you have to. You will see a small pin connecting the band to the buckle on either side of the band. Carefully use the the forked end of our band change tool to depress the spring loaded pin from the buckle to the band and release it from the buckle. When the tension on the spring pin is released it may pop out of the band and you will want to take care not to lose it.
Take the new band and slip the spring pins into the end of the band where it attaches to the buckle. Working with one end at a time, slip one side into the pin hole in the buckle. Use our band change tool to depress the other side of the spring pin and guide it into the pin hole in the other side of the buckle body. You will hear an audible "click" when the spring pin pops into place.
Sometimes the ends of the spring pins are exposed through holes on either side of the buckle. If this is the case simply use the pointed end of the band change tool to press out one side of the spring pin.