Insert your finger or the flat edge of a spudger into the small divot along the edge of the battery just below the battery cover lock.

Slide the spring-loaded switch with the battery symbol toward the center of the battery with one hand, while you pry the battery up with the other.

If you have correctly released both of the switches that hold the battery in place, it should be very easy to pry up.

Don't pry aggressively at the battery. If you can't hold the switch open while you pry, have a friend hold the switch while you lift out the battery.