I use PhotoPrint Pro in CS5, the plug-in is installed in LR4 but I can find no way of using the Canon tool.
Is it possible? If not why is it installed?
I do not know your special plug-in,
but the usual ways to access *all* plug-ins is via File menu - Plugin-Extras - one of the entries to the right.
If your desired plug-in does not show up there, you need first to invoke the plug-in Manager from the file menu to ensure it is really installed.