To create a new course click on the New Course link and you will be redirect to a page were a form to create a new course is presented:
The Course Key field is a unique identifier that will identify the course. When creating a new course revision then this validation will not be checked.
The Course Name is the name of the course.
The Course Information is for describe the course, html is fine here.
The Assessment ID select box is to associate the assessment that the users will have to answer (Enroll button) to perform an specific action. Here only the assessment that the user has created or has received permissions on will be shown. If no assesment is associated then no user can enroll to one course.
The Categories select box is to select to wich category the course will be shown in the index page. To create a new course version click on the icon on the left of Course Key information and change the fields you want.
To create a new course version click on the icon on the left of Course Key information and change the fields you want.
When creating a new course version the new information will be shown in all the site, you can change between all version.
Also you can categorize your course latter if you didn't categorize it in the first place by making click in the course name ( redierects you to Course description) and then by making click on the Categorize button.