Play around with the Banks and Librarian buttons in the SoundTower editor and you should be able to figure out how to load a sound bank in. In Windows at least for me, SoundTower wants to load things of its own custom file types, but you're probably dealing with sysex files at this level, so I typically have to choose *.syx from the file explorer dialog box to import those types of files.
You can also email their support to ask, I've had positive interactions with their support team.