The steps to use the console are as follows:
Step 1: Stop the server.
Step 2: Install Rocket Mod following this guide.
Step 3: Edit Rocket.config.xml in Configuration Files and enable RCON (set to true) and set a Password (Rcon port will be two ports above your game port. If your game port were to be 27015, Rcon port would be 27017).
Step 4: Start the server.
Step 5: Download putty from here.
Step 6: Open putty on your computer and connect using your server Ip and port. Use the Telnet protocol.
Step 7: Login with the password you set in step 3 (example: login h4v0c).