How can I add a section to a questionnaire?

There are several "extra sections" that get added to questionnaires upon creation. These extra ones are hidden by default and you can find them at the bottom of the list of sections for your questionnaire:

To turn them on you can click the toggle to open the section, and then click the blue "edit" button on the right hand side.

Then you can change the title, the order of where it sits on the listing of sections and turn the visibility to "always".