just solder the wire like this, it's your board, just verify on the progskeet that you are soldering to the exact point. soldering to ground is the same as soldering to sbe , just set the correct switches on the e3 and flash, and when you are done, desolder the wire. EDIT: @xAfgkiller96x , here another pic. as you can see there are more ground points (GND) , pick the one that is the easiest.
