Soldering!

The most fundamental skill needed to assemble any electronic project is Soldering. Like any skill, It takes some practice to perfect. The art is to form an electrical connection, using a molten mixture of lead and tin (solder).

Voltage; Most irons run from the mains at 240V. However, low voltage types (e,g 12V or 14V) generally form part of a soldering station and are designed to be used with a special controller made by the same manufacturer.

Wattage; Typically, they may not have a power rating of between 15-25 watts or so, which is fine for most work. A higher wattage does not mean that the iron runs hotter, it simply means that ther is more power in reserve for coping with larger joints.