First line up the stabilizer ends with the stabilizer holders and slide each end through the stabilizer holders connected to the palmrest.
Place the key on top of the plastic bracket and press down. If both plastic brackets are on correctly and securely, the key should easily snap into place.
Check if the key is secure by tapping around all sides of the key. This is a good test to make sure the metal clips are properly securing the plastic bracket, the stabilizer, and making sure that the plastic bracket can hold the key correctly.