Which step you don't understand? Lets discuss here.
Download the 1.0.4 zip package here
Extract the zip package
DELETE the install directory from the zip package
RENAME the admin directory to the same name as your current admin directory
PERFORM A FULL BACK UP ON YOUR SITE
TURN OFF ALL CACHES ON YOUR SHOP and SET IT TO FORCE COMPILE
Upload the files that are remaining from the zip archive to your site
Go to the config directory and edit the settings.inc.php file, update your version to 1.0.4
Go to PHPMyAdmin or you MySQL interface and run the query in this file here
Go to your modules directory and DELETE all of your stats module except statsdata and statsmodule. Also delete the modules graphnvd3, gridhtml, pagesnotfound, and sekeywords.
Now log in to your back office, the upgrade should be finished
Go to your modules page and install the module labeled Stats Module