At the rear of the server you will see a LAN port labeled ILO. The ILO works as long as power is connected, even if the server is off.
If not configured, ILO gets a DHCP address and have a default password that you can find on a pullout tab.
Connect LAN with a DHCP server enabled, point your browser to the default name and log on.
Name and password is on the tab, user is Administrator.