NOTE: Your MiFi may have come with a pre-installed SIM card.
Lift the tab at the edge of the battery cover and remove the cover.
Remove the battery from the battery well.
Lift the SIM access tab from underneath the white arrow and move it to the right.
NOTE: The MiFi PRO M4 supports only Nano SIM cards.
Slide the SIM card into the slot notch first, with the contact points facing down.
Close the SIM access tab, place the battery in the battery compartment and replace the cover. The SIM card MUST remain in the SIM card slot when in use.