I'm having trouble getting the engine to start and idle

Sir, it appears from your first post that you have much to learn about motorized bicycles. However you indicated that you want to learn so I will suggest that you start by using the search feature, type in keyword/s and look for information. There is a lot of it here.
Your problems are common and have been discussed and covered numerous times and I'm sure you can find some help if you search for it.

That said, let's see if we can at least get you headed in the right direction. From your description it sounds as if you have ignition. That's one of the three things necessary for the engine to run. The other two are air and fuel in the proper quantities. You can check for fuel flow to the carburetor from the tank by disconnecting the fuel line from the carb, opening the fuel petcock and seeing if fuel flows in a steady stream from the fuel line. If not, your problem might be a clogged fuel inlet inside the tank. This is common and why we recommend an in-line fuel filter between the tank and carburetor.

You'll want to make sure the fuel tank cap is venting properly. A cap that doesn't vent will stop the fuel flow after a few moments of running. Try running the bike with the cap loose to see if that could be part of your problem.

Clutch operation. You need to hold the clutch lever in, clutch disengaged, until you have pedaled up to about 10mph before releasing it. When coming to a stop, or slowing below about 10mph you must disengage the clutch (squeeze the handlebar lever) and hold it until the bike is again exceeding 10mph. The engine will not idle or run with the clutch engaged and the bike slowing or stopped.

Use the choke if necessary to get the engine running but then it should be off (open, lever down) after a few seconds. If the engine will not run with the choke open this might be an indication of a large air (vacuum) leak somewhere downstream of the carburetor or a severe lack of fuel.

Hard clutch pull can sometimes be the result of the clutch cable being routed where it has sharp bends or kinks. It must have large, sweeping curves and not be tied to the frame or other places too tightly. The clutch actuating mechanism inside the cover where the engine sprocket is must be lubricated. Oil won't do it. There is a cam, a steel pin called a bucking bar and a ball bearing inside that cover. They all need lubrication with a good grade of bearing grease. The cable itself will also benefit from lubrication.

Idle speed screw. They are a special screw and can not be replaced by a standard machine screw. The original has a small diameter pin protruding from the end of the threads. That pin engages a ramp on the throttle barrel and determines idle speed by blocking the barrel travel. A standard screw will either not reach far enough or too far and jamb the barrel from moving properly.

I hope some of these suggestions offer you some direction. Let us know how you're doing and if you make any progress.

Tom