I built a BT interface for a friend that have a Skoda Yeti and had to add a BT pairing buton that would fit in the dashboard.

Assembly is pretty straight forward, the micro switch is inserted in the body ("corps"), locked in place with a tab ("clavette") and the actuator is fitted on top ("tige-bouton"). The body is inserted in the housing ("capot-cahe") and the push-button ("bouton-l") is inserted last and should lock in place. To secure it you can add a drop of glue.