I made a minor error in my description above: Since the "Manage Add-Ins" page involves the installation of custom code, only Host (SuperUser) accounts can access it. So, you must be logged in as a SuperUser in order to access this menu item.

Andrew Nurse
DotNetNuke Core Team Member and Reports Module Project Lead
Microsoft Certified Professional Developer

So I solved my own problem.  It turns out the "Manage Add-in" option is only available in the "Edit" mode of the page, and not "Design" mode. 

I am now having another problem with the Report Services Visualizer.  I have it installed, I have created a report on my report server and set up the report module on a DNN page to use the report services visualizer.  When I load the page the visualizer finds my report and properly prompts for parameters, but when I click "View Report", I get nothing, no indication that the report is running, and no report shows up, just an empty module window where the report should be.  Any ideas ???