Hello Joan
Cant find a GX 50 on the link you posted, however I assume it has some form of LCD display, and that the Floppy is an external plug in unit, if so then you may find that when you select save or load (And the Floppy drive and disc is plugged in) the option to use the internal memory or floppy will appear, thus giving you a choice of where to load or save to.
If nothing shows up, then try and find the basic settings screen and see if there is an option to enable an external floppy drive.
Hope this helps

Bill