A soldering iron must be used to melt the solder connecting the battery to the motherboard.

A guide of how to solder can be found here: How To Solder and Desolder Connections

Cut the wires of the new battery to an appropriate length and strip the ends of the wire casing with the razor to expose the wire.

Solder the new battery to the motherboard.

Be sure to connect the correct wires to the correct points on the motherboard, or else device will not work.