I’m not sure where you can go wrong here, but anyway …
Assumes Sysex Librarian is 64bit
Connect DEVICE in USB Midi (not OB) mode then launch SL
- Select Device from drop down
- Drag and Drop sysex file to window
- Go to Device System Menu, select OS Upgrade, then press Play
Backup first (e.g. using record (one/many) feature of Sysex Librarian)
Do so at your own risk, there will be a Catalina version of Transfer in due course no doubt, so you could just wait if you’re unsure