The IA OPC Server is a package of a lot of OPC Servers. If none supports your PLC, you have to use other OPC Server. You cannot add one to IA OPC Server. It can't be upgraded.
NI recently released DSC 8.5 module for LabVIEW. In this module, there is a new OPC server called "NI OPC Server". Here is the list of all the PLCs it supports.
http://zone.ni.com/devzone/cda/tut/p/id/6417It seems that your PLC is supported. But this NI OPC Server can only work with DSC 8.5.
Contact your local NI people for more information.
Another choice is to use a 3rd party opc server.
Ryan Shi
National Instruments