How to make yourself Admin in Essential Mode.
Open FiveM and connect to your game server.
Press up arrow to see your in game id
Now stay in game and open your IceCon
HOW TO USE RCON WITH FIVEM SERVER
Click Connect then enter your server IP and Rcon Password
Once you are in enter command
Inside the command box type setgroup 1 superadmin
Where 1 is your game ID. If you have other ID than 1 use that instead.
Once you are done go back in game and try using admin commands.