Let's see if I can put it in words simpler.
4 trays total.
Only 2 leads from your ionto device, positive and negative.
Top 2 trays for hands, bottom trays for feet
2 top trays need a wire that connects both of them together
2 bottom trays need a wire connecting them together. This makes 2 trays act as one tray. Instead of one big tray. You are splitting them into 2 with a wire between them to conduct the current.
Treating 4 limbs at once does require more current. If you are using 2- 6 volt batteries at 1 or 2 more.
Hope that helps. I posted pictures somewhere in the back posts.