First, pull off the writing part by grabbing the pen at the back, and with your teeth, grab the pen where it starts to taper. pull it out, and once its out, take the tapered part, and ink cartridge first, hit it on a desk until it comes out. now, you should be left with a writing piece, a grip thingamajig, and a blocked off tube. take the writing tip and insert it, ink cartridge first, into the blocked off tube. hit the writing tip on the desk by holding the tube. after a few hits, the end should pop off.