Go to "My Account" (which can be seen across the top of the page when you're logged in).
Click on the title of the Hub you want to delete. Make sure you click on the title and don't click on "edit" right next to it. If you click on "edit" you won't see the "delete" option that way.
Once you've clicked on the title your Hub will appear, as will the option to delete it.
(You'll see a bar across the top that says "This Hub" and then the "edit", "delete", etc. buttons)