QUsb2Snes alone is pretty useless, it comes with various application that you can found in the application menu. Magic2Snes is special application, the best way is to refer to Magic2Snes
This application allows you access your SD2Snes files and perform some special operation, like starting a game, applying a patch.
This is one of the original application written by Redguyy, the Ui is not very fun, you can try your luck with QFile2Snes to have stuff like drag & drop.
The application will not work with something else than a sd2snes as files make no sense in other devices.
This application allow you to have a look at various memory of your SNES and overwrite value if you want.
This is patched NintendoSpy that use some memory value of your device to display the buttons your press. It has some limitation like not showing input during screen transition and such.