hmm, upon looking at that site, it says the resistors have ohms and stuff...... i slept through most of 8th grade science class, how are the ohms important?
ok, ill try to make this easy to understand. you know what the 12volt and 5 volts lines are, so thats a start. the most basic formula in electrical engineering is V = I * R. V is potential (measured in volts). I is current (in amps, or milliamps, whatever the case may be) and R is resistance (measured in ohms) you lets say that you have a 12 volt system. if you have a 4 ohm resistor in there, your equation looks like 12 = I * 4. you can use a little simple algebra, and you get a current of 3 amps. if you increase the voltage, and dont change the resistance, the current (I in the formula) has to increase in order to keep the equation in balance. a resistor just "resists" the flow of electrons through it (or the flow of electricity throug it), usually dissipating the extra energy as heat. this resistance to the flow of electricity causes a "voltage drop." this is why adding the resistor on the 12volt line causes the voltage to drop from 12v to 5v that the led wants. i hope i didnt confuse the heck out of you with that
. good luck!