I've attached a picture of what I think the schematic ought to look like. I didn't include a transformer because I don't have a symbol for it handy.
The SCR will trigger when the gate to cathode voltage (the two wires sticking up) exceeds the threshold.
For the love of cheeseburgers with mustard, please don't plug anything into this that you hold dear to your heart. At least not on your first attempt.
Check the capacitor you are using to see how much reverse voltage it can handle. It might be a good idea to add a second snubber diode hooked right across the cap's leads. This is not necessary in a perfect world, but parasitics can really get you in this high di/dt environment.
I might have read your link wrong, but I think that SCR is only rated for 16A.
Tape your experiments!