yes thats the way it is ment to be. But if you simply run a wire and leave the other wire still powering the coil - the tacho wont work.

Easiest way to say to do it is;
Take the +pos wire off the coil. Join a length of wire to it. Run it up to the tacho and through it. Then run it back to the coil and join that end to the coil +pos.
Simple.