If you need to adjust the number of sections in your course, here's how:

Add Sections

With editing turned on, scroll to the bottom of your course home page and click on the Add topics (or weeks) link. In the Add topics dialogue box, enter the number of sections you want to add, then click on Add topics.

Delete Sections

Sections have to be deleted one at a time. To delete a section, click on the Edit link associated with it, then click on Delete topic. Repeat as needed until you have the desired number of sections.