Adding Vertical AddThis Bar

I am trying to install the vertical addthis bar. I have the code but I don’t know where to put it. Specifically. Just telling me to put it into the code somewhere doesn’t help. Where exactly do I install it? I’m concerned that I’m going to put it somewhere is doesn’t belong and corrupt the code.

http://wordpress.org/plugins/addthis/