To replace the filament in the printer, the nozzle must be preheated to 200°. This will allow you to remove any remaining filament from the previous spool! Press the "filament release" button (found near where the filament spool is placed) and, with that button pressed, start extracting the old filament. Once done, place the new filament where the old one was taken out, in the same way: with the nozzle hot and the filament release button pressed, insert the filament through the corresponding hole. Continue inserting the filament until you see the "melted" filament coming out of the tip of the nozzle .