How to install AddThis plug in

To be honest my main question is how to get any plug in to work; without getting the site to crash. I have tried to add ADDThis and Google analytics and they both crashed the site. I realized I could ftp in and remove that plugin file to get the site to work again.

I would really like to have a social book marking tool and integration with analytics (I did get my site to verify so I can see analytics from Google’s page)?