The simplest and easiest switch to use is the SPST switch. SPST stands for Single Pole, Single Throw and represents the common on/off switch. As the lever moves from the off position to the on position, the internal contacts close. This allows current to flow through the circuit and powers the device connected to the switch. Whether you are connecting the SPST switch to exterior lights on your car, a device on in model railroad or turning on an LED on a breadboard, the connections are all the same.
Turn off the power to the circuit. Determine the location and install the SPST switch.
Route the wire to the SPST switch. If the wire is in a different location than the switch and it will not reach the switch, extend the wire by splicing a new piece onto the wire. Determine the additional wire length needed. Cut a piece of wire one inch longer than needed.
Strip a half inch of insulation from the four wire ends. Use your finger to open the copper strands on the wire. Slide on end of the new wire into the one end of the existing wire. Twist the copper strands in a clockwise direction to temporarily hold the two wires together.
Place the soldering iron on the wire splice for three to five seconds. Feed the solder into the copper strands and allow the solder to wick into the copper. Remove the soldering iron and solder. Allow the solder splice to cool naturally.
Slide a piece of heat-shrink tubing over the solder splice. Turn the hot air gun on and wave it over the tubing. The tubing will shrink over the splice and form a seal. Remove the hot air gun.
Continue with the other wire splice if needed.
Connect the wires to the switch terminals. It does not matter which terminal the wires are connected on, they can be connected to either terminal. If the wires must be soldered to the terminals, loop the wire through the hole in the solder tab and bend it backwards. Place the soldering iron on the tab for three to five seconds. Feed the solder into the connection point. The solder will wick into the wire and onto the tab. Remove the soldering iron and solder.