starter

My Mountaineer has been sitting since gas went up. The battery was going down so I put it in the garage on the charger. I tried to start it recently and the whole electrical system goes out until I disconnect and re-connect the battery. Same thing when I jump it across starter relay. Friend told me to jump it across the starter solenoid, but that sucker is buried. Do I jump it from the hot wire to the frame, or from the battery to the starter? Or from Charger to the starter?