The SHN Utility Suite talks to the powerline through an EZBridge/EZServ device or a PLC. If you have an EZBridge/EZServ device, you have established an IP address for it, either by defining an explicit IP address or having your DHCP server dynamically assign it. It is this IP address that goes into the “EZBridge IP Address” field. If you do not have an EZBridge/EZServ device, you do not use the “EZBridge IP Address” field.
Without an EZBridge/EZServ device (which is the majority of folks using Insteon) you click on the “Use PLC” button and then click on “Connect”. A message will be displayed on the bottom of the Utility screen when a connection to the PLC has been established. You do not need to enter the xx.xx.xx address of the PLC, the Utility finds it automatically. The xx.xx.xx value of your EZIOS8A is not entered until you get to the configuration screen for EZIOxx devices by clicking on the EZIOxx tab at the top of the screen.
EDIT: There is a later version of the Utility available (1.73). I would suggest getting the latest level of the Utility.