New horn, how about wiring?

[vefferdk]

Hi.

I have bought a Ford A horn, and wants to have an extra button for it, but my question is, how hard is it to get a wire from out front and into the cabin?

I can't seem to find any sorta holes or ways to get it trhu..
Its an Mk1..

Anyone who can explain to me where or how I do this, as easy as possible?

Thanks ;)