Radiator adjusting

I have old style radiators which are not heating up correctly and am getting completely flummoxed by how to adjust them as neither end has a white cap, just the metal showing which is the same both sides.

I assumed that the left hand side was to let hot water in and the right to adjust the heat. I have turned them all right up on the left and reduced them on the right but still can't get one of the downstairs ones hot at all - although the pipe is hot and I keep on bleeding them. This one has a thermostatic valve on it, but doesn't make any difference whichever way I turn it

I am a complete novice at DIY (but willing to have a go!) and would really appreciate some advice on what I should adjust to get the house warm.

Thanks very much and apologies if this is a really girlie question!

when you turn on the heating the pipe to the valve which warms up first is the flow, this is the one you turn to adjust the heat. The other is the return. Turn the flow valve anti clockwise comletely to leave it full open and turn the return valve back half a turn from fully closed then bleed the rads making sure the pump isn't running.

Open both valves on the radiator that doesn't work, and close one valve on all the others to see if that makes the problem one heat.