After removing the striker assembly, you pull the spring and its guide fron the firing pin. Stand the spring assmbly on its end and pull the spring down so you can remove the weight ( the round pc on the end with a cut out on the side ) and it should fall off the guide. If you are still holding the spring down, then take 1 of the BT caps and slide it between the guide and the spring. You may need to push the spring further down for this. Then install the other side and you're done.
Be sure you glasses and work in an area that you can find something easily if it flys off.