This is how to open the upper panel of a vertical piano. First, you need to open the top lid/cover of the piano. Refer to the image below.

Look inside the piano cabinet. At the corners, you will see locking mechanisms. Unlock them by turning clockwise or counter-clockwise to release the locks. See the images below.

Once you have already unlocked the locking mechanisms, you can now easily lift the upper panel off the piano. Be careful because it might be quite heavy.

After removing the upper panel of the vertical piano, the piano should look somewhat similar to the image below.