Wiring a light socket that doesn't have screws
If there is only 1 set of wiring coming to this fixture use the back stabs (I hate back stabs). If there are more than 1 set pigtail and then use back stabs. This is one of the few places I have used backstab fixtures. I would never use the back stabs to jumper the sets, if the pigtail is used the only power being used is by the fixture itself. I have not had any problems with pigtails and back stabs but using the fixture as the jumper I have seen hundreds of failures. There should be a strip guide on the fixture strip the wire to that length. Push the wire into the round hole . this can normally only be used with 14 awg wire. If no strip gauge strip between 1/2 to 3/4 inch if copper is showing a piece of scrap wire or a small screwdriver can be used in the slot to remove the wire and trim it off and verify that no copper is showing and you should be good to go.