Replacing receptacle wallplate with nightlight, but terminals are not exposed
This is a cheap outlet that only uses backstabs for connections, no screw terminals. You will need to replace the outlet with one that has screws.
Turn off the power and unscrew the outlet and pull it out of the box. Get a small screwdriver and insert it in the slots in the back of the outlet by each wire while pulling at the wire. The wires should come out. Shepard hook the wires and screw them into the new outlet, black wires to brass screws and white wires to silver screws. You can also pigtail the wires if you have some extra wire and some wire nuts.