You can use thumbnail or guitar pick to open it.

The battery is easy to be removed.

Remove this covering strip.

Release the LCD Screen flex cable.

Undo 10 screws.

Loosen here.

Heat up for a while.

Use guitar pick to make a gap.

There are sticker underneath, cut it up carefully.

Keep cutting up sticker at the range.

Keep cutting, or they would adhere together.

Try to insert deeper.

See? there's a gap.

Keep trying.

Do the same to another side.

Now we can try to remove the Back Frame.

There is sticker underneath.

First tear off the protective film.

Now put it back.

Press to set it right on the position.

Connect the LCD Screen flex cable.

Put back the Battery.

Power on the phone.

Input test code.

If you heard music, it works! Turn it off.

Put back the covering strip.

Tighten up 10 screws.

Press sides to set it well.

Source: Youtube