Gadgets Manual

This procedure requires the following tools: Clean non-marring work surface
Preliminary Steps
Warning: Always shut down the computer before opening it to avoid damaging its internal components or causing injury. After you shut down the computer, the internal components can be very hot. Let the computer cool down before continuing.

Procedure
Warning: If the computer has been recently operating, allow it to cool down before performing this procedure.
Shut down the computer.
Disconnect the power cord and any other cables connected to the computer.
Place the computer face down.
Slide both battery latches away and lift the battery out of the battery bay.

Get pdf MacBook Pro Battery Replacement Instructions (DIY Manual)