The adapter includes an embedded modem installed at the factory.
Remove the SIM door.
Insert an activated 4FF-sized SIM card into the slot marked SIM1 with metal contacts up and notch in. It clicks into place. Depress again to remove, if necessary.
Use the SIM2 slot for a secondary/backup, as needed.
Replace the SIM door and secure with the door screw.
Important
Please note that modems do not power themselves off when the SIM door is removed. If you need to swap SIM cards between the two slots, or replace one or both SIMs on a powered device, Cradlepoint strongly recommends that you power off the W1850 before removing the SIM door. Re-attaching a SIM door on a powered device automatically resets the modem, and you must NOT power off your device during a modem reset. Powering off your device during a modem reset can cause the modem to become unbootable.