To delete a project, you must be an Account or Organisational Administrator. For more information on this, please consult the User permissions article.
As Project Administrator, select the project you'd like to delete from your dashboard and then access 'Settings' from your sidebar menu, then choose 'Delete' as seen below.
Now select the big red 'Delete' button and that's it.
NB Only delete your project if you're sure you won't need any of its contents ever again! You can always delete individual files from a project via the Footage page...