It is now time to solder the wires in to their correct locations. To do this hold the wire on the old solder, using a small amount of solder melt the solder and wires to the old connection points.

The black wire on the - location and the red wire on the + location.

Soldering irons are very hot and can cause serious injury. If you do not know how to use a soldering iron please seek help from someone who is experienced.

For an explanation on soldering refer to iFixit's soldering guide How To Solder and Desolder Connections