I have a popping cracking noise in light switch, how do I replace it?

First of all if it is popping and cracking I wouldn't use the light switch. There is either a wire loose or something is shorting out and could cause a spark. Replacing a light switch is a very easy fix. Every light switch package has the exact instruction in it as to where the wires go. First you need to turn off the power to that area from the fuse box. Then take the cover plate off and unscrew the switch from the wall. One of the easiest way to replace it is just take the new switch and hold it the exact way as the old one. Just move the wires from the old switch to the new one in the exact location they were. If you want to verify that you have it together correctly either you or someone else can turn the power back on, flip the switch to make sure it works but when you replace it in the wall make sure not to touch any of the metal from the wall box and wires on the switch. You could get a little zap, just enough to make you jump a little, or short something out. But not likely to really hurt anything. Just be carefully and replace all the hardware. Easy - peasy you did it.

This is a fire hazard. Call an electrician.

http://www.dummies.com/home-garden/home-improvement/lighting/how-to-replace-a-light-switch/

https://www.youtube.com/watch?v=imia1J7a8No