The idle mixture screw is located on the side of the carburetor next to the valve cover. Access to the screw is inhibited by the air cleaner. I find it much easier to remove the air cleaner and even then it is tough to get the screwdriver tip into the screw head.
removing the air cleaner? not really. If you unplug the vacuum line between the Hot Idle Compensation valve and the tee above the PCV valve, you should plug the open port on the tee.
Screwing the idle mixture all the way in (clockwise) will seat the screw and stop the flow of gasoline through the idle circuit. Turing the screw clockwise leans out the mixture.
Also remember the idle mixture screw is only for idle condition. As you drive and put a load on the engine there are...