How to wire electronic switch?

Looks like the H03 has a lighted E-SW. 3 wires? Unless you wire in a resistor you will not be able to use the LED on the SW. Also make sure you are using the 2 correct pads for the SW. Not the LED pad. DMM will indicate to you if the pads are correct as you push the SW.

While not specific to this light, I was able to get the L6 Lighted E-SW working with D4 firmware from info in this thread. Ignore the SMD resistors added to the driver but you get an idea where to mount the Esw wires to a driver. MtnE 20mm is not identical but very similar.
To get the LED functional on the esw, you will need to find a connection from the POS spring on the component side of the driver. Also put a 10K to 20K resistor in line to the LED pad on the Esw.