Turn off power to the system and wear the anti-static strap for ESD protection. Secure the M.2-SSD by the card edges and align the "keyed-end" to the socket on the system motherboard, while tilting the mounting -end upwards slightly.
Gently push the M.2-SSD into the socket while placing the M.2-SSD mounting-end onto the stand-off or mounting bracket. Secure with screw or clip, depending on the hardware type.