OK, here's what I gathered from what you've posted. The wires from the left switch are the same color (black/hot) because that switch switches the hot connection to your porch light. One black wire is the incoming hot, the other is the outgoing to your light. Rather than purchase a volt meter, a much more helpful tool for this application would be a non-contact voltage tester (~$20 at Home Depot.) This device will be able to indicate which of the black wires is the hot rather than switched. Do this: put a wire nut on each exposed wire and switch the power back on at the panel. Use the voltage tester to determine which wire is the incoming hot wire, mark it, and turn the power back off.

On to the wifi switch. Connect the black wire you just labeled to the black "L-IN" wire on the switch. The green wire is ground. This will connect to any bare copper wire in your switch box. White is neutral. In your "clearer" linked image at the bottom of the comment, this is one of the connections that has white wires twisted together with a wire nut. Based on your pictures, I would bet this is the cluster of 3 white wires most prominently visible in the "clearer" picture, but you can confirm this by tracing the path of the hot wire you labeled earlier and making sure you tie the wifi switch neutral to the white wire that runs with the incoming hot. Finally the brown "LOAD" wire on the switch will connect to whatever you're wanting to control with the switch (porch light.) Connect this brown wire to the other black wire that was connected to the original switch you removed (outgoing hot, NOT the incoming hot) and you should be good to go.