The battery is located just to the left and below the RAM slots.

Note the positive is to the right and negative to the left. There is a + sign located on the logic board to the right of the battery.

Care must be taken when removing the battery to prevent it dropping into the machine. It pulls straight out. Use a small instrument like a dental pick or flathead screwdriver to lift the + end out. I use a large hemostat to hold the battery.

After removal of the old battery and replace with a new one by pressing it into place.

Replace the access panel. Turn it over and plug it in. Start up and go under the Apple to System Preferences - System - Date & Time. If you have an internet connection check the box to automatically and select Apple Americas.

If no internet just set the date and time manually.

Next select the Time Zone box. Click the curser on the map to the closest city to you.

Next click the Clock box and select the type of display you prefer.