Wiring Shelly Uni to water level gauge 240-30 ohm

Have decided to try some DIY and bought a Shelly UNI to which I aim to connect a level gauge to be able to get a reading on the water level in a tank.

Got me one of these Nivågivare holdingtank : Nivågivare för septitank 12/24V ...

The q is how to wire, have understood it as its not “just to connect” but I will need to add some kind of resistance? could someone either help me “as a dummie” or point me in the direction to where I can learn how to do it?

Would be very much appreciated.