How to Turn On a Wall Heater

The click-click-click sound is probably coming from the water meter.

Check if it makes the same sound when you run COLD water, in a kitchen sink, for example.

Sometimes a mixing valve is used to put some hot and some cold water into the toilet tank to prevent or limit the tank sweating in the summertime. The mixing valve is adjusted to "temper" the water by adding just enough hot water to raise the temperature of the water in the tank from cold, to I'd say "lukewarm", but not hot. The water is then much closer to room temperature, so it won't "feel" hot, or even particularly warm. If a mixing valve is installed and the water feels hot or even particularly warm, or even on the cold side, the valve needs to be adjusted.

In either case, cold water only, or a mixture of hot and cold, some water meters just "click" as they measure the amount of water flowing through it.

Baseboard heaters work largely by convection--the heating of air by the radiator fins causes a rising action, and a low pressure zone below. That zone must be replenished. Ideally, open space below allows a "chimney effect" to occur.

However, since you say that the downstream end of the pipe is room temperature, all available heat is already being extracted, and therefore no efficiency stands to be gained.

I'd test that, though, to be sure. Take an accurate temperature reading at the downstream end of the system, and if it's more than about ten degrees above ambient you have more heat available to be released with better airflow.

If you can't get the property owner to assist, a small fan directed at the heater would provide adequate airflow to extract additional heat during very cold spells.