If you don't have a soldering iron or gun and you don't want to spend money buying either of them to solder, then you can use a lighter. The flame of a lighter has a similar temperature of a soldering iron tip and it can melt flux solder without a problem. Before soldering using a lighter, make sure you adjust the flame so it is a blue colour and not orange, this is by using the flame adjustment slider located near the button that ignites the lighter. The reason why you should adjust the flame to a blue colour is because it is hotter than an orange flame and it will melt solder quicker.
So if you want to solder electrical wires with a lighter, simply ignite the lighter and point the flame towards the flux solder wire and let it melt onto the braid of the wire, this is to make a solder joint. When soldering electrical wires using a lighter, make sure the flame of the lighter doesn't burn the insulation casing off the wire.