To delete a project, open the project and click the Actions button in the upper right corner of the page header.
The Actions menu includes three options:
Select Delete Project.

You will be asked to confirm the deletion by typing the word DELETE in all caps.
Once confirmed, the project is permanently deleted and cannot be recovered.
If you are unsure about deleting, choose Archive Project from the same Actions menu. Archived projects are removed from your dashboards and no longer count against your plan's project limit, but the data stays intact and you can restore the project later.