GLAST events can be accessed using from HepRep XML files or from a GAUDI server, which includes a HepEventServer. To access this HepEventServer select Open Data Source... from the File menu and select the HepRep CORBA Servers wizard.
Paste the IOR from your HepEventServer in the IOR or URL field and click Add to List. You may give it a different name than New Node of course. New servers are added to the top-level, and only visible to you. You can then select the new server, see its status/description and click Finish to open the dataset for browsing.