Go to the address http://192.168.4.1 in your web browser. The browser should ask for a username and password, the login is root and the standard password is ecowifi! (with exclamation mark at the end).
If the password has been changed and you don’t remember it, you have the option of resetting the Eco router and the username/password will be reset. Resetting the router is done by turning the router off, and then keeping the WPS button pressed while turning it back on. As soon as the power light starts flashing, you can release the WPS button.
This will return all router settings, including wifi network name and wifi password, to standard values.
You can find the complete manual here.