Dell 1125 Mono Laser MFP User Manual page 29

2. Remove the Drum Cartridge by pulling the green handle toward the front of the printer.
3. Hold the drum cartridge in one hand and push the blue toner release lever in the direction shown to free the toner cartridge.
4. Hold the replacement drum cartridge in one hand and push the toner cartridge into the drum cartridge in the direction shown until it clicks into place.
5. Insert the drum cartridge into the printer, using the guiding slots to correctly position the drum. Slide the drum cartridge into the printer until it clicks into
place.