Like most basic phones, you can push the entire cover and slide it off. Pushing on one specific location doesn't always work, but putting pressure on the whole cover and then sliding it down will work. It will slide down just a bit before coming off.
Another way is to press the cover and the front of the phone and then slide them in opposite directions until the battery cover releases. It's hard to explain but you can feel the battery cover slip off when you push it against the rest of the phone in the opposite direction.
