You will have to bleed them and may have to prime the master cylinder. Google search, there are different ways to do so. I think it is also in the service manual. If there is no evidence of leakage in the carpet or down the firewall, you most likely have a leak in the tubing to the rear, and could be "anyplace from the master on back. By the way the FRONT fitting on the master feeds the REAR brakes.
Thanks I’ll look into bleeding the brakes. I got a service manual on the way too, so that’ll be very helpful once It’s here. I am aware that the front fitting in the master cylinder is for the rear, and that is the one that is empty.