you need a worker name and worker password in your suprnova account

Follow this getting started guide: https://xmg.suprnova.cc/index.php?page=gettingstarted

For commands, it tells you right there: /minerd -a m7mhash --scrypt -o stratum+tcp://xmg.suprnova.cc:7128 -u Weblogin.WorkerName -p WorkerPassword