You can only delete your content module when there is no submission data associated with it (no Learner has started an exercise created from your content module) or when it is not being used as an active or upcoming exercise in an existing Group.
Expand Content Module Details
Go to the Library page. Select the downward facing arrow associated with the content module you would like to delete.
Delete Content Module
From the drop down, select Delete on the bottom left-hand side. Your content module is now deleted.