To access the IPMI Web GUI, please connect the IPMI port to your network, then go to:
Bios -> IPMI -> BMC Network Configuration and grub the IP address for the IPMI if you are using  DHCP setting, if you are using static setting then you can just use the IP you have set.
After that open a web browser on any connected computer (this has to have access to your network) and enter the IPMI IP in URL bar and you will see the login screen, then enter your user name and password to login.