If filament from someone else is currently loaded, navigate to the unload filament option, then select the type of filament you will be loading. Wait for the hotend to heat up and click in the stick to unload when prompted. Be sure to insert the end of the filament into the retainer on the spool. Insert the new filament, carefully feeding in until the extruder gears grab it. Follow the remaining instructions on the controller to complete the load.