Google Analytics Not Installed

I am trying to install Google Analytics and I’m getting real confused. I first tried to use the Google Analyticator plug-in and kept getting the “Status: Tracking Not Installed” message. I then did a search in this forum and got a lot of confusing suggestions. They all say to deactivate the plug-ins (which I did) and then they start to deviate.

I am running Aspen-child theme on a multi-site. One set of instructions says to add the tracking code just above the </head> tag on the header.php file in my child theme. Now, I’m already confused since my child theme has only one file the style.css file. So, I added the code to the header.php file in my Aspen theme directory. It didn’t work. I have no caching active so it’s my understanding it should work right away. When it didn’t work I removed it. I really don’t know where to put this code.

Also Google says to insert the code in every page I want to track, which is quite a few, including many posts on sub-sites. Is there a tutorial somewhere I can read to help me out with this? Or can someone give me a little guidance?