1995 Oldsmobile 88 All interior electrical systems appear d

In Janurary I was idleing the car to warm it up. When I got in the car the engine temp showed 200 on the dash but the heater was blowing ice cold. I had just installed a new thermostat and it had ben working fine for a week or so. When I put the car in reverse the engine died. When I attempted to restart, the ignition just clicked and would not crank. I assumed this to be either a starter or battery issue. The battery showed only 9 volts when checked, so I removed it from the car and had it tested at a parts house, it tested good and they recharged the battery. I was injured before I could put the battery back in the car, so the car has sat without a battery for the last 3 months. Now, I have finally been able to try and get the car running. I have again recharged the battery and have 13 volts at the alternator and at the starter. However the interior of the car is dead. The ignition does nothing when turned over, no dash lights, no radio, no headlights, no nothing! Could this be a fusable link, computer, relay, or what? I'm at a loss for what to do next. Please Help! The car ran great prior to this.