POT's aren't particularly practical for dimming LED's. About 90% of the travel of the POT will be useless and the LED will go from full brightness to complete darkness in that 10% range in the middle, but it will work. Use a 1K pot for each LED. One end of the POT gets connected to the + of the battery, the other gets connected to the - end, The lead in the middle gets connected to the LED's anode, and the cathode of the LED gets connected to the - lead of the battery. Also use a resistor in series with each LED to limit the current when the POT is at one extreme end of it's travel. That resistor value and the wattage rating of the POT's you need to use depends on the voltage you're going to be powering the LED's from. I would recommend using a 10 turn POT to give you at least some chance to be able to set a specific brightness to the LEDs.