Step By Step
1) Download the latest update version for your website from the www.joomla.org website.
2) Unpackage the Joomla update file in a folder on your computer using a program like WinZip.
3) Backup your Joomla website.
My favorite tool for Joomla backup is XCloner.
4) Connect to your website via FTP.
My favorite tool for FTP is WS_FTP Home.
5) Upload the Joomla update files to the root of your Joomla directory.
6) Overwrite the files when prompted by the FTP program.
7) Log into the back end of your Joomla website and check that the new version number is showing.
8) Visit the frontend of your website to make sure everything is OK.