when creating a report, you can set the contexts where it is made available. Possible options now are Product, Project, Home, Library, QMS, and Part
according to the help, part should add your report to the Part more details page. However, this seems to be a bug in WT, a remaining of the old Windchill.
PTC will remove this, but this is functionality that everyone is waiting for:
make it possible to display your report, or to start your custom report from the part's information page. This option should add your custom reports to the "Reports" ribbon menu in the details page from your part.
see also case 12967262