what's the deal with sin? How did it get here? How do you get rid of it?

Okay sit down this might take a while.
A long time ago back at the start of the world God made man and later woman..they were perfect...sinless...and free. God told them not to eat from the tree of 'knowledge of good and evil' or they'd die. Because God knew that Man was happiest when he could walk and talk with God and not have any barriers between them. Now here's the twist. The bad guy, Satan, comes in and figures "hey i'll just get them to disobey God and then they can follow me and I'll be king instead of God". He must have rubbed his hands with glee. The snake goes over to eve. And since she'd never seen a talking snake before I guess she figured she'd better listen to what it had to say. "you won't die, don't be silly. God just said that to frighten you. you can be king like God and know everything if you eat this fruit." So since Eve looks and the fruit and it looks pretty good she eats it and gives some to Adam.

So there you have it. Satan fools Adam and Eve into thinking they know better than God and they disobey him. This is where sin comes into the world. from this moment on we can no longer live in the garden of Eden nor have such a close relationship with God because our sin has torn us away from Him.
You see God knew best right from the start. He had something much much better in mind. He wanted us to be able to live with Him perfectly and freely forever.
So in order to do that. God gives up the most precious thing he has. His only son. He says "I love them so much, I'm goign to send my son to die in their place. So that they don't have to." Jesus died the worst death you can imagine, we made his life pretty hard by putting up all sorts of barriers so that we would have excuses not to listen to what he had to say, we would torture him, spit on him, argue with him, kill him, just so God could do exactly what he wanted to do. Have his son die in our place. The only way you can get rid of sin is to make sure you get rid of the sin in your own life. apart from that its up to God.
But its not all bad. In return for believing in Him, trusting him, loving him he gives us so much more in return.