The construction of the IR illuminator is pretty simple as all it takes is connecting the battery to the IR LED Ring and using the switch to open and close the circuit. Most of these LED rings have a 2 prong connector that wires can be soldered to pretty easily, and the LED Ring has a built-in light sensor that cuts off the circuit in daylight in case you forget to open the switch. The LED ring also has the necessary components to keep the LEDs from being damaged by too much current (resistors).
A typical LED circuit is shown below and is one of the easiest circuits to make. Just follow all polarity rules (+ voltage to + voltage) etc. and everything should work just fine. There are many web sites that have plenty of electronic hobby information out there. Remember Google knows all!
Assembly Notes:
1. Ensure the positive (+) lead of teh 12 VDC power source is attached to the positive (+) terminal on the IR LED RING.
2. The Switch does not have any polarity.