The program is pretty straight-forward: fill out the form, then press the "Create Tier" button. The tier will appear in a new window, and you can save the tier as you would any other web image. To make filling out the difficulties a little easier, the program automatically adjusts the difficulties to conform to RB3 conventions: basic and pro drum difficulties will always match, for example. One useful thing to remember is that if a song has harmonies, you should set pro vocals first; basic vocals will be set to match. If you want to turn off this feature, just uncheck the "Apply RB3 Difficulty Rules" box.
Please let me know if you run into any problems using the program. I don't know if I'll have time to make improvements to it, but I welcome any suggestions.