I just had an IM chat with Matt Mower, the developer of the excellent liveTopics tool, and he kindly helped me - the Radio Userland and blog newbie - through getting setup with the topics you see on this blog. If you are on Radio, visit Matt's page and get his tool.

I was getting an error after having installed the tool, and the google macro was not working. Matt said:

Yes I think the error is likely because you do not have a Google API key
installed in Radio.  Assuming that you are comfortable with Radio (or
Frontier) Please follow the instructions at
http://radio.userland.com/googleApi and everything will probably start
working once you have finished step 4.

Then I asked about if liveTopics indexes the stories on the blog, rather than just the entries. His thoughts -

...my advice would be to create a post as a summary of the story and attach the topics to it. ... It's likely that, if they're interested enough to see the summary, they'll click through.

Thanks Matt!