Have a project / workspace you don't need anymore?
You can delete or archive a project by clicking the ‘Settings’ icon at the top right of your board and then choosing ‘Admin Options’ on the left. Select the "Archive" option from the top of the list or the "Delete" option at the bottom.
NOTE: Bringing a project out of archive is fairly simple whereas deletion is permanent, so delete only when you must.
Here's a short video tour of the process: