Unscrew and remove the cover.

If you want to add a RJ45 jack but only have the first outlet, that you can’t replace, to work with, you can just mount the new outlet next to the old one. You’ll need to connect La to 6 and Lb to 5. You can use any kind of shielded twisted pair cable to wire the new outlet.

Remove the the connections.

Keep track of La and Lb. You’ll need to know what wires to connect where in the new socket.

Unscrew the socket from the wall.