The InSite upgrade files are available from Customer Portal (If you are a registered user).
On Customer Portal home page, select Service & Support > Prepress Software Downloads.
In the Filter by Product area, select Unified Workflow > Portal Products > INSITE Prepress Portal System > 11.5.
On the Downloads page, click the IPP 11.5 Installer link and download the InSite_11.5.0.##.zip file to the J:\InSiteStuff folder on your InSite server.