Support the lower control arm or axle housing with a floor jack to relieve tension on the shock mounting bolts.

Back off the spring preload collar; Turn rebound clicker counter-clockwise 2–4 clicks.

Retorque hardware immediately to 85 ft-lbs. Replace heavily oxidized bolts. Comprehensive Troubleshooting Manual

Locate the Schrader valve or needle port on the shock reservoir/cap.

Your BR 3021 shock manual likely ends with a maintenance log. Follow this schedule:

Set the dial to 4 clicks open from the full stiff position.

Monotube gas-charged / Coilover configuration (depending on specific vehicle application)