1. Remove the dust cap.

2. Flip the chair on its back.  Remove the fork stem nut and remove the fork.  

3. Install the new fork through the caster housing.  Install the fork stem nut and tighten.  Do not over tighten the fork stem nut. The fork should swing freely, but not be loose in the caster housings. If the fork flutters in use, tighten the fork stem nut.

4. Install the dust cap.