Spondoolies who ran myminer.io is no longer trading as a company, so the myminer.io site no longer works

The miner should pickup an IP address from your router automatically.

Check your router DHCP table and see what the IP of the miner is, then put that IP address in your web browser.

Also check the Spondoolies thread for more help, this question has been asked many times before. https://bitcointalk.org/index.php?topic=521520.0