In order to work, an inverter has to be hooked up to the car battery in some way. Some of the most common configurations include:

• fuse panel
• direct to battery
• cigarette lighter
• 12v accessory socket

The easiest way to hook an inverter up is to simply plug it into the cigarette lighter or another 12v accessory socket, but there are some limitations to that type of setup.
Since there may be other components hooked up to the cigarette lighter or accessory circuit, there is an inherent limitation on what type of devices can be hooked up to the inverter.

Inverters that are connected like that are generally limited to a 5 or 10 amp draw.

In heavier duty applications, the inverter needs to be connected to the fuse panel or directly to the battery.
Some fuse panels have empty slots that an inverter can be wired into, which will provide a dedicated circuit to the device.
In other cases, the inverter can be connected directly to the battery with an in-line fuse. In either case, it is vital to use some type of fuse to avoid a potentially hazardous situation.