The circuit diagram is a follows

Here's a quick explanation of what it's doing.
The two ouput lines from the switch are held 'low' (i.e. at logic 0) by the 2 resistors until they are connected to +5V by the swithc.
The output for the JP10/11 pair is the inverse (1 for 0, 0 for 1) of the output for JP6/7. This configuration gives Japanese for the top switch setting, American when in it's centre off position and European in the bottow switch setting. The completed board should
look something like this



Now you need power for your circuit, you take this from the Saturn's board. Again with the board upside down and the joypad ports pointing to your right, look at the top right hand corner of the board. You'll see 5 large soldered pins, this is where the powersupply connects to the Saturn board.
From left to right, the pins are +12V, +5.2V, +5.2V , Ground , Ground

We need +5.2V and Ground, so solder a wire onto the second pin from the left , and another wire onto the last pin on the right.



You'll notice I've soldered 2 lines onto the +5.2V pin, this is because you'll also a +5.2V for the 50/60Hz switch later on.


The complete country circuit including power should look something like this