Bhopping is a technique for ghosts to reduce visibility when moving. To bhop, hold ctrl and press s and space bar at the same time repeatedly. This technique doesn't work forwards. After about 2 hops back, you should go faster.
You install it and click the shortcut on ur desktop when ur done installing (i'll assume you're talking about the video game) ...Why are you even asking this?
You can get a MP5 with a silencer in the item shop, and in the future they will come out with more, but if you see guns with silencers not in the item shop, it's a hack and report that hacker.
you could easily glitch by running up to a wall, and press ctrl. But now mostly all the glitches are patched, and the ones that are still live, aren't released.