I doubt there's a bleed for the system, just empty it by removing the plug at the bottom of the radiator, let the liquid out (it's only a mix of water and anti-freeze - and probably a bit of rust and sh*t it has picked up during its life going round the system). Put the plug back in tightly then refill until it reaches the top where the filler cap is. Turn the engine over, turn it off and recheck to see if it needs topping up. Then after a short run letting the engine get up to temperature recheck WHEN THE RADIATOR FEELS COOL ENOUGH!!!! Top up if needed. You cannot overfill it and it probably won't make any difference if its not totally full, there's an overflow bottle that allows a little expansion and contraction of the contents. EDIT - Remember to replace the fluid with the correct mix of (I think its ionised) water and the correct antifreeze. This is important to use the correct one as it can corrode the matrix if not causing failure in the future.