To use IVT Bluesoleil 8.0.395.0, users need to activate the software using a valid activation key. The activation key is a unique code that unlocks the full features of the software, allowing users to enjoy all the benefits of IVT Bluesoleil 8.0.395.0. Without a valid activation key, users may be limited to a trial version of the software, which may not offer all the features and benefits of the full version.