How should i start?

What are you trying to accomplish?

First, consider what you want to connect with the wires.

I am reminded of this, from the early days of computer games: You are in a room. There is a door, a knife, a gold plate, and a book...

The first thing you should do is take a course in electrical safety! Using a stainless steel cabinet without any explanation of what you are building disturbs me. I imagine you are building a test project or science fair project. The line voltage powering your transformers and heaters must be safely grounded in case of a short to the cabinet, etc.

Please inform us all of what you are making so we may help you build it as well as save your life!!!!!

AS always, begin at the beginning, learn something about a subject, before you begin to build your dream! "Or not" just go waste your time learning the hard and often expensive way!

TMF

l'd suggest that you start wiring by hiring an electrician or someone with a clue. That way you will not kill your stupid ass. And we won't have to read another headline that says "Dumbass KILLS Self Farting Around Where He had No Business!"

Flip a coin. If it lands on heads, wire the thermostat to both fuses. If it land on tails, wire the secondary of the transformer to the cabinet. It it stands on end, pray about it.

Seriously, draw a schematic and start in the top left corner.

S

P.S. Share the schematic with us and describe your project in detail.