I need help : my car wont start.

It was automatic, I've changed it for standard. Everything was ok untill last saturday.

It does the same thing as when you try to start your engine without pushing the clutch : nothing, not even a "click"

So I want to bypass the usual wiring to the starter and use an independant button.

This is where I need help : I don't really know how ??? I'm ok with mecanic, but not with electicity. It would be very nice of you to explain precisely what to do, what cable I should use, things I must be carefull with, etc...

Thanks in advance !

 

I'd start by testing the clutch interlock switch.
Backprobe it with an ohmeter or continuity tester & work the pedal.
Some spray contact cleaner there & in the ignition switch may help