I eventually found where to set up the instal/update proxy settings and was able to get to the installation page.
Unfortunately, I'm getting an error "Serena Team Plugin (3.0.1) requires plug-in "org.eclipse.team.core (2.0.0)", or compatible.
At this point, I know it's beyond the realm of SE issues. I'll sort this out (hopefully).
Given the choice between SE as my editor or PVCS integration, I'd take the former; I may have to figure out how to uninstall the Serena integration.
Unfortunately, this is my first venture into RSA after decades as a Windows programmer.