Should my od light be lit always or should it be off
meaning not visible how am I to drive it with it lit or
The OD light on means the over drive is off. Push the button to drive with the OD on which is the normal way to drive.
In your car, I believe the light means that the overdrive is off. When you engage the overdrive button on the gearshift, the light goes off. All the options, settings, and maintenance requirements for your vehicle are covered in your owners manual, available on line, just google your vehicle.
To be clear - OD light is ON then the OD function is disabled. OD light OFF is normal driving mode. Toggle between the two modes via the OD switch on your shifter. OD ON is used primarily for towing.