Put the needle clip onto the needle and drop it into the slide. You will notice indents in the slide where the needle clip fits, without blocking the hole for the throttle cable.
Then drop in the silver washer type thing and tap the slide untill it seats sitting on top of the indentions.
The throttle slide has a notch where it fits into the carb body so it has to be in the right position or it won't slide in.
Sorry about the music, I didn't think the camera would pick it up that loud.
Heres the breakdown http://www.mopedriders.org/html/manuals/puch/sm/puchsm057.jpg