Remove the bottom dust cap.
Split the locking nut with a 8mm Allen key and 22mm spanner.
Split the two locking rings with C spanners.
Wind them right down to the bottom to release the tension on the spring.
Release the bottom rod and wind all the way in.
Carefully separate the shock from the body taking care not to damage the seal.
You can now remove the spring.
When repacing the spring, turn the shock on it’s head, slide over the new spring, seat and helper spring then the body. Apply some downward pressure on the body to help relocate the threaded rod through the bottom. Now tighten the lock rings on your Ohlins shock.