Open the hood and then remove the hood-to-cowl seal (the long rubber strip). You should find some 5/16" screws under the rubber, remove them. Next, remove the two hood stops. Finally, remove the wipers. After this, the cowl cover will lift up and you can get to the leaky area. If the cause is rust, the JB weld will be a temporary patch at best but it should hold until you can get some POR-15 and fiberglass to patch the hole.