This is going to be a bit of guesswork but, here goes. The relay with 4 terminals will have two "control" terminals and two "controlled" terminals. When you turn on the lights via a switch, current is sent to the relay. This current in the relay energizes an electro-magnet that closes the two "controlled" contacts. I would say that the "S" contact would be wired to the Switch and the "G" contact would be routed to Ground. The "B" contact would go to a voltage source - or Battery - and the "L" contact would go to the Load - your driving lights.
When you turn the switch "on", the relay energizes and the "B" and "L" contacts are connected, thereby sending voltage from the battery to the lights. The driving lights would have to be grounded through their mounting bolts or a separate ground wire run from their base to a suitable ground.
Hope this helps.
