Your interface has two main sections.
On the left, is the Table of Contents (TOC). This shows the headings and subheadings of the course. Clicking on a heading will expand the section, showing you the sub-sections.
On the right, is the Viewing Area. This is where you will view and interact with the content of your course.
You can collapse the TOC, by clicking on the double-arrows in the upper right of the TOC.
Clicking the double-arrow will reveal the TOC again.
When looking at the TOC, you will see:
Headings that are highlighted in orange are the active section and subsection. Essentially, 'you are here'.
An orange 'tick' mark, on the right, indicates content that you've already viewed.
A paperclip icon, on an orange background; on the left, indicates that there are downloadable files associated with this section.
When content that has associated downloadable files, you will also see a paperclip icon in the upper right of the Viewing Area.
Clicking on this 'toggle tab' will reveal files that you can download.