This is not a complete “HowTo”, just some info to get you started.
The command to use is getbeaconbeststatedetail
This command will return the current state of the beacon and with that the lists of nodes that are waiting, selected, earning.
In Postman you can run this code:
{
"id": 1,
"jsonrpc": "1.0",
"method": "getbeaconbeststatedetail",
"params": []
}
by https://mainnet.incognito.org/fullnode
More in-depth information on the function itself can be found on Github