Before attempting to remove a nozzle, you should ensure any filament has been removed from the HotEnd. You can do this manually or by setting up some custom G-code as outlined here.
1. Wait for the HotEnd to cool to room temperature.
Always wait for your HotEnd to cool to below 50°C before attempting to change Nozzles
2. Unscrew the Revo Nozzle from the Heat Sink.
There is no need to use tools, this step should be done using only your hands.
3. Screw the new Revo Nozzle into the Heat Sink.
The Nozzle only needs to be 'finger tight' and hot-tightening is not required.
4. Happy Nozzle changing!