Unscrew the three black, 4mm screws with a phillips screwdriver size PH 0 (one of which is under the gold colored ribbon cable.)

Unscrew the three gray, 3mm screws with the same screwdriver (phillips screwdriver size PH 0.)

Unplug the connector the connects the battery to the mother board.

Make sure to use a plastic opening tool instead of a metal spudger to avoid any unnecessary accidental shorting out of components.