RAM 1500 Owner's Manual page 43

THINGS TO KNOW BEFORE STARTING YOUR VEHICLE 41
To Lock The Vehicle's Doors
With one of the vehicle's Passive Entry RKE transmitters
within 5 ft (1.5 m) of the driver or passenger front door
2
handles, press the door handle LOCK button to lock all
doors.
Incorrect Way To Grab Keyless Enter-N-Go™ Door Handle
Outside Door Handle Lock Button