1. While standing on a flat and stable surface, switch off the unit and remove the plug from the extension cord.
2. Remove the 2 bolts and 2 nuts, then remove the steel blade blades.
3. Clean the drive shaft with biodegradable oil.
4. Place the new blades onto the drive shaft so that the holes on the axles line up with the holes on the drive shaft.
5. Insert the 2 bolts through the holes and secure them with the 2 nuts.

You can find these inscructions with instructional diagrams in the product manuable, which can be downloaded above.