Observe the correct alignment for the metal brace. The brace must sit tight in its dedicated, raised rack.

Place the keycap over the top of the hole, and push it down gently. Unlike the other normal keycaps, you should feel some resistance when doing so.

Now, push the keycap with greater force until a click is heard.

Check that the key moves as one, by pressing with your finger on its left and right hand sides to confirm that the key moves effortlessly without obstruction. here is web > keyboardtestt.com