1. Download SteamCMD. 2. Execute it. 3. Enter login anonymous. 4. Enter force_install_dir and here put the address where you want to install the server. 5.Enter app_update 4020 and wait 5 minutes. 6. Configure it as you want... the map,the gamemode,the amount of players, etc.... 7. Run start.bat and enter with the iP.
If you have any question leave it in you know where.