To remove the battery, flip the laptop over and remove the 6 screws from the base cover. Find and loosen the two screws at the back of the cover and gently pry the cover away from the hinges. Lift the base cover, identify and unplug the battery cable. Find the battery and remove the 3 screws securing it to the system. Lift and remove the battery.
To reinstall the battery, insert it back into the system and attach it using the 3 screws. Reconnect the battery cable to the motherboard and secure the base cover.