To upgrade manually, unzip this file and upload the contents to the root folder of your website (ie. the folder where Joomla is installed). This will overwrite just the nBill files. Next time you login and go to nBill administrator after upgrade, it will prompt you to click on a link to upgrade your database. You must click that link before the upgrade can be considered complete.
This patch is intended for upgrading between versions of the Standard edition of nBill - it is not suitable for upgrading from nBill Lite to nBill Standard (for that you have to install nBill standard over the top of nBill Lite - no need to uninstall first and you will not lose any data from nBill Lite, however, any customisation will be lost and the upgrade is not reversible so take a backup first).