Installing Google Analytics

I'm new to this whole thing, so please excuse the elementary question: It seems I am to put the tracking code for Google Analytics in the Header OR Footer section of "Webmaster Tools", but not both. How do I determine which I should put it in? Once I do this, is it all I need to do? Do I need to do anything with the "Tracking ID"? I just want to ensure I get data on all my pages/posts, and I'm not sure if that means I need to drop the code elsewhere as well. Thanks in advance.