Inactivating a chapter makes it unavailable to all users, however it is not deleted and can be activated again at a future time. (More information on this here.) If you wish to delete a chapter completely please see the page found here.
Selected the project name, click on "Chapter" and choose "View/edit chapter":
Click on the chapter name for the chapter you wish to inactivate.
After selecting the chapter, click on the "Chapter" menu and select "Inactivate chapter":
You will be asked to confirm.
After clicking "Inactivate chapter" you will see that the chapter now appears as (Inactivated):
The chapter will no longer be accessible (and will not appear for users) until it has been activated again. For information about activating an inactive project please see the information found here.