Your radiator appears empty because your cooling system has a leak.
It sounds like you might have a crack in your radiator or reservoir and will need to get it repaired or replaced.
Over-obvious answer? Your radiator, or one of your radiator hoses, leaks - badly.
If the entire system (radiator, engine block and heater system) is empty it will take 11 to 12 qts to refill (this also depends on what engine you have and if it has ac or not). If you only drain the radiator, aprox 5 qts.
Should be a plug at the bottom or rear of the radiator
pull the petcock on the bottom of the radiator. it's either on the feft or the right bottom
It is at the end of the lower radiator hose on the motor. You will have to empty the radiator and remove the housing to replace it.
On the drivers side under the radiator there is a small black knob-like thing that you turn, and it will empty the radiator. Do not turn too hard, it will snap.
The cooling system on this vehicle does not use a radiator cap on the radiator but on a remote tank. It may have a different (larger) cap on it than what you are used to seeing on the radiator.
It is possible that your radiator needs to be topped up or that it is empty. My little 1991 Mazda Autozam Revue did the same thing so i checked the radiator and both tanks were just about empty.
You shouldn't need to "bleed" the radiator in your Forester. If you top off the coolant in the radiator the next time you check the top of your radiator is empty again? You have a blown head gasket. Voice of experience here. --Ken
Check coolant in Radiator!!! Radiator might be empty, fill it, it's probably the reason why your engine is overheated
Empty the radiator - and re-fill it ! Car anti-freeze is added to the water in the radiator so, if you drain it and re-fill it, you can add a fresh quantity of anti-freeze into the radiator filler hole.