To replace the butterfly mechanism, first, verify that you are holding it the right way round and the right way up.

Position the bottom pegs in their clips and then, holding it in position with a finger, press each of the top two pegs into their clips.

To replace the key cap, carefully place it accurately in position and first press the top corners in order to engage the top clips. Then press the bottom corners to engage the bottom clips.

Check that the key cap is level, all four clips engaged and that it moves freely up and down.