Gather soldering iron, solder, wire stripper, helping hands, and heat shrink tubing
Unplug power and ensure the wires are not energized
Strip a small amount of insulation from each wire end
Twist stranded wire ends together if needed
Slide heat shrink tubing onto one wire before soldering
Heat the soldering iron and clean the tip
Tin the iron tip with a small amount of solder
Heat the wire joint, not the solder directly
Apply solder to the heated wire until it flows into the joint
Remove solder, then remove the iron
Hold the wires still until the solder solidifies
Inspect the joint for a smooth, shiny connection
Slide heat shrink tubing over the joint and shrink it
Use electrical tape if heat shrink tubing is not available
Test the connection after it cools completely