I assume you mean how do you get to the needle, right? You don't have to do anything with the lifter arm when you're working with the main jet.
You don't need to remove the lifter arm completely, just remove the screw on it so the arm is loose from the shaft, then you can push the slide up through the carb from the inside while you unscrew the 2 screws holding the plastic thing to the slide.
When you re-assemble it you'll need to take the plastic cover off the side of the carb and push the shaft in to get the hole lined back up for the lifter arm.
I think that's what you wanted to know, if it's not then rephrase it and i'll give it another shot.