Hold the motherboard by the corners and maneuver it out of its recess, being careful not to snag any cables.
Bend the fingerprint sensor cable slightly so that it bows upward near the connector.
Stand the motherboard up and position it such that the connector rests against the socket.
Use your finger to carefully align the connector and press it into the socket. Do not use excessive force! If done correctly, the socket should hold the connector securely.