Cradlepoint MBR1400 - Manual (Page 8)

6 SIM Card Installation (LTE version only)
1. Disconnect the modem from the router by pulling from side to side. If you
experience difficulty, apply slight pressure to the back of the device to facilitate
separation.
2. Insert SIM card in the slot in the modem (notch end first, it will click into place).
3. Reconnect the modem to the router.
4. Insert screws (3) to secure connection between router and modem (backside).
Step 1 Step 2 Step 3 Step 4