It's simple, instead of soldering the wire to pin 6, use the grabber and attach it to pin 6. As for pin 4, completely ignore it as it is ground. Ground is basically any metal part on your computer.
Get a potentiometer (pot). Anything above 40 kOhms will do. I'm using a 500 kOhm pot.
The pot should have to two wires connected to it - The wire with the grabber on it that goes to pin 6, and a wire that connects to ground.(Again, ground is any metal part of your computer. In my case, I connected ground to the screw that keeps my hard drive in place.)
Borrow someone's multimeter, then measure your pot to MAX resistance (you will have to measure it in Ohms - The Ohms symbol looks like a set of headphones).
The red wire from the multimeter connects to the grabber, and the black wire from the multimeter connects to the ground wire. Once this is done, turn your pot so that the multimeter reads 0. (0 = MAX resistance, 1 = No resistance)
Once that has been done, connect your pot like I stated above. Grabber goes to pin 6 and the other wire goes to ground.
Before you start measuring voltages, turn your computer off and clear the BIOS. This will default the VDimm to 2.55 Volts.
Take your multimeter, and switch it to DC 10 Volts or 20 Volts depending on the multimeter, then connect the black wire to ground, and the red wire to the leg of that chip right under the DIMM slots as shown in the picture. Your voltage reading should be at around 2.55.
At this point, turn the pot about 90 degrees to lower its resistance, then measure the voltages again. They should have increased slightly. Do this until you're satisfied with the voltage output. (I added 0.2V - so my voltage readings were showing as 2.75)
If you did it like I did, for evey voltage setting in the bios, you add 0.2 Volts. So if your Vdimm is set to 2.65 in the BIOS, you will actually get 2.85.
EDIT: When you're measuring resistance, make a note of which direction the pot has to be turned in order to increase/decrease resistance. In my case, turning it clockwise increased resistance, reducing voltage. Turning it counter-clockwise reduced resistance but increased voltage.
Somebody please correct me if I'm wrong, but I'm 99% sure I did it this way.