I answered on the other thread too but . . .
The bleed valve is top right of the radiator. Long time since I did it but I seem to remember it's a screwdriver you need. Might be an Allen key. Just loosen it and air will come out.
If no air escapes then you might have a pressure problem on the boiler.
If the boiler pressure is too low then the heating won't work properly.
Make sure the boiler is turned on to heating whilst you are trying all this - otherwise there won't be any pressure to force the air out.
Hope this helps