Remove every SIM or SD card from the slots.

Unscrew all the six screws from the top plastic cover.

Start to lift gently the cover using opening picks from its bottom-right corner.

Keep pushing the opening pick along all the external sides of the plastic cover.

You need to open all the plastic clips hidden under the cover itself. You can notice a soft "pop" when opening successfully one of them.

When all the clips are opened, you can lift the cover completely with caution.