To remove the battery:
Make sure your device is turned off then gently remove the back cover then lift the battery by the notch to remove.
To install/reinstall the battery:
Remove the back cover and align the battery’s exposed metal contacts with the battery connectors at the bottom of the compartment in the phone. Insert the battery, contacts side first, and gently push the battery into place. Battery should lie flat within the compartment or the phone may not operate properly. When finished, replace the back cover, pressing along sides to make sure the cover is fully in place. Connecting parts will snap audibly as the cover is pressed back into place.