AWStats Config File Location
The AWStats config file is located in the '/home/yourusername/tmp/awstats/' directory (or just 'tmp/awstats' from your home directory). It is called 'awstats.yoursitename.conf', where yoursitename is the name of your web site and yourusername is the name of the cPanel account you are under right now.
You have located the file, you download it to your computer, you edit it and you upload it to the server again and you believe that you are done.
This will probably not work because in most installations, cPanel reinitializes the AWStats configuration file every day, just before it runs the stats update.
Change the File Permissions
This first solution is obvious, but it does not always work. Connect to the site with FTP and try to change the permissions of 'awstats.yoursitename.conf' to read only (444). If this does not work, please try changing permissions using the Legacy File Manager.