How to connect a difavtomat for a boiler?

Help connect the case with the difavtomatom to the outlet instead of the old machines. The photo shows how it is installed now, from the machine there is an extension cord into which the boiler is connected. I want to put a case with a difavtomat and connect a moisture-proof socket for the boiler from it, but I don’t know where to connect the phase, where to zero, where to earth. Explain on the fingers, the ability to call the master is not. Thank.