OpenWrt has a web admin GUI called “LuCi”.
You need to use the “root” password to successfully access LuCi, 'root' is the default admin account of your OpenWrt device. On a freshly installed OpenWrt device, there is no password set yet for the 'root' account, you can just enter right away. Please make sure, to set an individual 'root' password as soon as possible.
If you are unable to access your OpenWrt device, due to messed up IP address/root password configuration, refer to the troubleshooting section of the user guide, to reset the OpenWrt device's settings.