The soldering iron can destroy components on the motherboard. Only touch the soldering iron to the solder already on the board.

Touch the tip of the soldering iron to the solder connecting the negative wire.

Pull back on the wire with the iron in place, removing it from the hot solder.

The solder will be melted almost instantly. There is no need to hold the iron on the solder for more than a second or two. Visit iFixit's soldering guide for more info.

Repeat this step for the positive wire.