I have installed the plugin and enabled it, as instructed, but nothing shows on my articles. I was wondering, since it's plugin, is there some code I should put in articles to show navigation?
There is no code needed in the articles. The navigation is shown under the same circumstances where the native Joomla navigation appears. To test it, enable both plugins and see what happens.
The articles have to be arranged in a "browsable" manner, i.e. through a menu structure or blog architecture.