Lie the cover beside the phone upon removal. Your assembly should appear as shown this far.
Insert the plastic opening tool into the crevice between the camera and the battery of the phone. Using a gentle prying motion, lift the end of the battery and remove.
After removal, recycle the defective battery appropriately. Take the replacement battery and lie it near the phone as shown. Your assembly should resemble the presented picture. Note that the cover is not included in this particular photo.