In your server.cfg file add the following line:
seta rconpassword "your password here"
You can add your IP to your favorites list in game and then click on it and click "password" there you can enter it so everytime you join your own dedicated server you won't have to enter it.
Of course, you can enter the password in game (after you've set it in the cfg file) by typing:
rconpassword <your password>
(in the console)
Then when you type commands in the console, just type \rcon before the command.