- Open LaunchBox
- Go to Tools -> Manage... -> Emulators
- Click Add to add an emulator. Don't worry about the Application Path parameter. It's enough to just input RetriX.UWP.exe
- Click Associated Platforms, and make sure "Default Emulator" checkbox is checked for platforms which should be started with RetriX Gold. If "Default Emulator" is not checked, then RetroArch is used instead.