Ok well, i bought an add-a-circuit so that i can use a previous existing fuse in the box. What i want to know is, which one is the fuse for the headlights if i want the cathodes to turn on with its switch?

If i don't use that, i want my own separate switch. I used this computer hookup molex connector i had, cut some stuff off so it's like this now.

Switch------------red wire------------------transformer plug
switch-----------yellow wire----nowhere transformer--------black wire---for ground

How do i get the power hooked into the fuse box but to let the switch control it? Can the yellow wire do that? the switch is 2 prongs, 1 with a red wire 1 with a yellow.

 

AFAIK, attaching the add-a-circuit to the fusebox will not mean that when headlights are on the cathodes will come on.
I used a separate switch. What you need to do is connect the addacircuit to any fuse slot (I used 9) and crimp a wire (preferrably a red one) onto add a circuit. Solder the other end of that wire to the middle contact of the switch. Now, solder the transformer red wire to any open contact on the switch. Finally, run the transformer black wire to a ground.

You may have to extend the transformer wires. If so, extend the red and black ones, not the wires going to the tubes.

I'm not sure what the yellow wire is for.