First go to http://www.dip.co.uk/Support/Support-Login.aspx and log in with your Serial Number and Licence Code. This will take you to the secure download section. You need to download the full version.
Once you have this saved on the server machine, shutdown the BACS.IP Server application and run the downloaded executable file. This will take you through the installation. When this is complete, log in to the Administrator with the "firsttime" account (just press OK).
If you have installed the new version of BACS.IP in the same path as the previous version (by default C:\Program Files\DIP\BACS.IP) you will now be asked if you wish to set-up a fresh system or perform an upgrade. Select the Upgrade option. This will import all of your File Formats, users etc.
Once the Server installation is complete, you will need to install the new version of the BACS.IP client applications on any other client machines.