Upgrading your Magento store to a new version is most easily done using the Magento Connect Manager.
First, log in to your Magento Administration Panel, then click on System | Magento Connect | Magento Connect Manager. Now log in using an account with full administrator privileges.
Note: If this is the first time you log in to Magento Connect (i.e. no packages are listed under the 'connect.magentocommerce.com/core' channel), you will need to prepare the downloader by typing "magento-core/Mage_All_Latest" in the Extension Key field, and then click on the Install button. Once the initial setup procedure has completed, click on Refresh.
You will now see a list of all the Magento packages currently installed (see Figure 1).
Figure 1: Magento Connect Manager
Click on the Check for Upgrades button to have Magento automatically search for available upgrades. After the search is complete, available updates will be highlighted in yellow. Now, select the "Upgrade to .." option in the Actions drop-down next to the package you are upgrading (see Figure 2). To upgrade the entire Magento application and all core modules, you just have to select Mage_All_Latest, and all the requried packages will be upgraded.
We recommend that you check the "Clear all sessions after successful install or upgrade" checkbox to avoid problems with cached data later on.
Click Commit Changes to start the upgrade process.
Figure 2: Select the appropriate package to upgrade
The application will now start downloading the required files and upgrade your Magento store. You can follow the progress in the status window at the bottom of the page (Figure 3). You will be notified once the upgrade process has completed.
Figure 3: Magento upgrade procedure completed
Congratulations, you have now successfully upgraded your Magento store to the newest version! You should be able to refresh the page to see the changes. The current version number is also shown in the footer of your store Frontend and Admin pages.
If you experience any problems during the upgrade process or have any questions, feel free to contact our support team for assistance.