How can I change plastic filament in my printer?

First heat the extruder to a suitable temperature (PLA = 190°C), extrude a small bit by hand (turn the large gear clockwise), release the butterfly bolt, push the EXTRUDER BEARING CLAMP back and in a smooth motion pull the filament out of the extruder. Now you can feed new filament in, tighten the butterfly bolt a bit and extrude until the nozzle is filled with the new material.