can anyone guide me on setup?
In data multicast, all devices must be in same local network. Usually you can share the network on one device for all others.
Enable Data Multicasting on all running RealDash instances and make one (and only one) of the instances Host.
Now you need to select on each instance of what data will be shared by that instance. That is done on ‘Settings->Data Multicast->Select Multicast Values’. Try first with sharing a RPM from the instance that is connected to your vehicle to verify that other instances will receive the RPM correctly. Then you can start adding values to the list as needed.