You need to have teacher-rights to edit a course site. In your workspace, click Turn editing on.
This will open up the set of tools necessary to edit the course site.
There are several ways to organise your workspace.
Customise your workspace
You can use the template workspace to share your content, all materials in one section and all activities in another.
On the course home page, you can share the basic info about the course.
Time-based and theme-based workspace
You can also add and rename sections (see how) and organise contents according to the course timeline and/or the course themes.