How do I add a legend to an ArcGIS map visualization?

Thanks for the article link. It says to click the Show Layer Legend button but I don't see that button anywhere when I click the yellow Expand Map Tools button. I can get as far as shown in the photo below. However, that isn't a proper legend. I need a legend that is properly formatted and that I can move to the best location on the map, and preferably without the expanded yellow buttons list. Also it has a No Value entry which is bad since (i) all the plotted locations have values , and (2) the No Value symbol is indistinguishable from same-sized symbols with values.

Kia ora, the link no longer works