Operators can run admin commands such as gamemode, time and ban. Because you may not be an operator yet when you first join, use the panel console.

1. Open your server in the panel  and go to the Console tab.
2. Type op YourUsername and press Enter. Do not add a / in the console.
3. The console confirms the change. If it says the player does not exist, check your spelling.

To remove operator status, use deop YourUsername.

On Bedrock servers, edit permissions.json or use the same console command if your server software supports it. On servers running a permissions plugin such as LuckPerms, grant permissions there instead of using vanilla OP.

See also: Basic Server Commands.