You install the upgrade by unzipping the downloaded zip file (e.g. using winzip from www.winzip.com) and then copying all the files within the zip file into the Crocodile Technology\PlugIns\TechSupplies folder (exact location will vary according to how Croc Tech was originally installed).
When copying you will have to answer 'yes' when Windows asks you if you want to update files with the same filename.