Starter wire is black with blue stripe. (on older fords such as cossie's FRST's and ERST's etc, you don't say what car it is ??)

You need to be sure the button you are using can handle the solenoids current draw first !! if not you need to relay your button mate.

You need a normal 4/5 pin automotive relay.

Cut the black blue (starter wire) and connect one side to pin 30 and the other to pin 87 on ya relay.

On your switch connect one terminal to +12V (red wire in coloum, you should fuse your supply too), then the other switch terminal to pin 85 on your relay. Now just need a ground on pin 86 and ya done, if you've used a 5 pin relay just leave pin 87a as it's not needed.