I guess you are trying to upgrade to 1.7. You can install Magento Connect manager.You will be able to upgrade to 1.7 as well as install new modules or extensions using this manager and it comes free. But in case you have a live site I would suggest you to take back up prior to performing upgradation.
Here you can download the manager : http://www.magentocommerce.com/magento-connect/magentoconnect-manager.html
And here goes a tutorial to help you go through the steps : http://www.siteground.com/tutorials/magento/magento_connect.htm
But lastly I would recommend you to get the job done by some professional in case you have a live website.
Team Magento Portico