The first thing you should do when disassembling electronic devices in general is to disconnect it from any power source. Make sure the AC adapter isn't connected to the laptop before you start.

Turn the laptop upside down, with the battery side closest to you. Unlock the left slider by pressing it to the left. It will stay in this position.

Now slide the right slider to the right. This one won't lock in position, so you must slide the battery towards you while pressing this slider to the right to remove it.