(From v.9.0.1 )
Get the upgrade files. OK, you've probably already done this, but let's review anyway. The file you downloaded should be called tngupdate901-902.zip. Extract or "unzip" the files included in tngupdate901-902.zip to a temporary location on your hard drive. Some files should extract into subfolders called 'css', 'img', 'js', 'languages' and 'templates' (among others).
Back up settings and custom files, other preparation. | Show instructions
Upload them. Upload all the files and folders (except the "templates" folder, which will be covered later) to the main TNG area on your web site. For many of you, the main TNG area will be the "public_html" folder. Be sure to overwrite existing files that have the same names. Note: The folders contained in this zip file do not contain all of the files that are supposed to be in the same folders on your site. Only files that have changed since the last release are included. If your upload program will erase the unchanged files when you upload these smaller folders with the same names, then be sure to merge the folders instead.
Open this readme file from your site. If you previously opened this file from your local computer, close it now and open it again from your web site (for example, "http://www.mysite.com/readme901-902.html"). Use a browser, not an FTP program! The file should be among the files you just uploaded.
Update your template. | Show instructions
The update should be complete. You did it! If anything doesn't look right, please try the following before asking for support:
Go to your home page
Go to the Admin menu (address is now "admin.php" instead of "admin/index.php")