This is a simple process. Simply remove the DI cartridge from the housing. On the bottom of the cartridge is a screw-on cap. Unscrew it and remove the foam piece. Dump out the old resin into a garbage can/trash bag. Fill up the cartridge with the new resin and put the foam piece back in place. Screw the cap back on and you're done! CAUTION!! - Resin is a very round material. Be careful not to get it into your eye. If you do, flush out your eye for about 15-20 minutes. Also, if it gets on a hard floor, be careful not to step on it because it can cause you to slip.