Instructions
Turn the slide over so that you are looking into the bottom, then place the barrel into the front portion of the slide and push it forward until it stops moving.
Compress the recoil spring assembly and place it in the slide immediately to the rear of the barrel. Press the spring assembly down firmly, then release the tension on the spring so that it expands to fill its section of the slide.
Turn the slide over and place it on the rails on top of the Glock's frame. The slide should be placed at the very front of the frame.
Push the slide back on the rails until it clicks into place.
Rack the slide back once and dry-fire it--make sure that the pistol is unloaded before you do this--to make sure that all the pieces work properly.