How do I remove ignition switch on my 150 Tank scooter?

You'll have to remove the plastic around the ignition switch. There should be 3-6 screws holding this in place. Once removed, you will see that the ignition switch has a holding screw/bolt on each side (2). Once removed, the wiring will have a connector that needs to be disconnected. You can now install your replacement, connect wiring, two bolts, test ignition before replacing the plastics...