Strange. This is a single supply module, yet it has two switchers on board.
Anyway. Yes, connect a voltage between 3.5V and 28V to the input and measure the output voltage, which you indeed should be able to adjust with the multiturn potmeter.
Check the switchers' datasheets for the maximum output current. The right IC seems to be an LM25005, that can deliver 2.5A. May be a bit high for the coil though. The left one I can't read.
From the picture, it seems like You assume the circuit is a "black box" and connect the input and you should get a voltage at the output. The output voltage seems to be controllable via the small (blue) pot near the bottom of the picture.
What you have described is correct, connect the input and measure with a multimeter at the output and adjust till desired voltage is achieved. Though while connecting your actual load you might want to ensure the current drawn is within the acceptable range of the board :)