Place the spool on the right-side holder so it unwinds toward the PTFE inlet without rubbing the enclosure. Cut a clean tip and straighten the first section.
Select Filament > Load filament on the xLCD. Insert the filament into the PTFE tube under the right handle when prompted. The side sensor should detect it, after which the Nextruder takes over. Keep gentle pressure; forcing the strand can buckle it inside the tube.
Confirm the material type on screen. The printer heats to a suitable loading temperature, then purges. Answer the color question honestly and purge again if the old material is still visible. Remove the cooled strand only when toolhead motion has stopped.
To unload, choose the matching menu command and wait through the heating and retraction sequence. Pull the strand from the side path when instructed, rewind it under light tension and lock its end to the spool.
If autoload does not trigger, check that filament-sensor calibration has passed and that no broken fragment remains in the path. The Prusa CORE One support section separates side-sensor and Nextruder-sensor diagnostics. Use that distinction before opening the extruder.
Very soft filament may need the exact handling method Prusa documents for the material. Do not defeat a sensor simply to push past a resistance you have not identified.
Loading filament correctly matters most once slicing choices come into play, so the PrusaSlicer profile guide for the CORE One is a natural next stop for matching the loaded spool to a filament preset. For broader spool handling between prints, general filament storage guidance covers how to keep material dry and ready to load.