There are 3 common level sender signal types. Resistance based meters (0-240 Ohm I think) can be connected to the level inputs on the Ekrano. Voltage based (0-10V) and current based (4-20mA) need to be connected to the Victron GX Tank 140 device, which then connects to the Ekrano by USB.
I looked at the page you linked to but this did not state what type it is. I searched a bit and another Redarc gauge was listed as resistance based.
You need to confirm with the seller or Redarc what the measurement type is and what range of values. Then read the Ekrano or GX Tank 140 manuals.