The fan comes on by grounding the relay to it. Hot wire to the relay. I don't have the wiring diagram for yours but it may be labeled which is the common.
You can run a wire to ground or you can run a wire to a switch on the dash and then to ground so you can control it.
A typical relay coil uses tab #'s 85 and 86. One goes to 12V and the other goes to ground. If you pull the relay out of the socket, you will see the diagram on the side, and on the bottom where the tabs are, will be numbers corresponding to the tabs.