Step 2: Assembling the LED, Resistor and Wires:Cat two pieces of 30 Gauge wire, each 2 - 4 inches in length (4 inches is suggested). Solder the wires to the LED and resistor in the following order.
Wire - LED Positive | LED Negative - Resistor - Wire
{ + } --------[LED]-------|------////[47 Ohms]/////-------- { - }
The negative side of the LED is the shorter leg lead. You should end up with something that looks like this:

Solder the completed LED circuit to the controller’s circuit board. Make sure there are no exposed wires (Wires NOT covered by plastic insulation) exposed. If there is, any metal on metal contact can cause a short within the controller causing it to malfunction, fry out, and stop working.

This completes the more difficult part of assembly.
Step 3: Plastics Modification:
Grab the small piece of rubber with three holes in it for the Start, Select and PS3 Home buttons.

You will need to cut the white piece since it will cover the LED. The reason we are cutting it is it will press against the LED and wont allow you to put the controller back together properly.
Before the cut:

After the cut:

You will need to modify another piece of plastic as the LED legs will need to pass through it. Cut away as seen below.
Before:

After:
