So are you saying that when you click on "Select Printer Software" in the Print Using menu, the window that appears shows no printers? If yes, then I would be inclined to reset the printing system which I have detailed below. Note that this will remove all printers and scanners that you currently have listed in Print & Scan, so you may want to make notes of what you have and how you connect to these devices. And if you do have too many printers / scanners in the list that you don't want to remove just yet, then you could select the Generic Postscript driver that is listed in the Print Using menu. This will at least get you printing in the meantime.
How to Reset the Printing System
1. Open System Preferences > Print & Scan
2. Move your mouse over the Printers list
3. Hold down the Control button and click the mouse
4. Click the "Reset printing system ..." popup
5. Restart your Mac
Now you can try to add your FX printer again.