>>You computer probably came loaded with the web-based version. <<

It turned out that this is the case, and that the desktop software I purchased never loaded correctly.

Thanks to a chat session with Microsoft Support, I was able to install the Office software, which is indeed a desktop version.

Where I erred in my first installation was that the "loading" panel suggested that the download should take just a few moments. After I did not notice any significant progress within a half-hour or so I aborted the download and tried again. The second time I saw a prompt that Office had already downloaded.

With my relatively slow web connection [I did have the machine plugged into my router as opposed to using wi-fi], the download took more than 2 hours when Support helped me with it.

Thanks to all who responded and helped.