Kind of a vague question...
Are you trying to attach the Windows PC directly to the XServe RAID?
Or is the XServe RAID attached to a Mac and you're trying to access the data over a network?
In the first case you should just need a fiber channel card in the Windows PC and run a fiber channel cable from the PC to the RAID - depending on how the RAID is configured, it should just appear.
In the second case you need to share the XServe RAID volumes via SMB. The specifics of how to do this vary based on which version of Mac OS X Server you're running.