1. Unscrew the nozzle nut from the cutting head (not necessary to take the cutting head off). It looks like the picture shown below.
2. Take the retainer collet out from the nozzle nut.
3. Let the new nozzle go through both the nozzle nut and the retainer collet.
4. Put the end of the new nozzle into the cutting head then screw it back slightly until tight.
5. Install the whole part to the machine and it is ready to use.