Your machine looks like it was using gas. The tap on which you have the p-stat is for the cup warmer.
You should hook up the cup warmer as usual, for the p-stat use the fitting in the lower right hand side of the photo with the 3 chalk marks. You can see a line goes from the fitting to what appears to be a gas pressure switch. Remove the line that goes to the gas pressure switch and hook up the Sirai switch to that - unless of course there is a spare fitting somewhere. But don't obviously continue with your temporary connection to the cup warmer valve.