As many widgets are you want. Keep in mind, when embedding a widget, it is only for one topic, not the entire site. Additionally, if you'd like to embed multiple widgets, you can embed one-by-one or one widget after another.
If you'd like to embed a widget, in your Management Dashboard, the Topics tab will show you all of the topics that have been created. In order to embed a widget for a particular topic, select "Embed Widget" next to your desired topic and follow the HTML instructions provided.