To archive a project:
Go to the project dashboard and locate the project you wish to archive. This is found by clicking on the project name in the left sidebar of your dashboard or by doing a search of the project name in your library.
Select the project to open the project dashboard.
Click the gear/settings icon next to the project name, then select to ARCHIVE.
The project can be unarchived at any time by finding the project in the ARCHIVED PROJECTS section of your dashboard, selecting the same gear icon, and opting UNARCHIVE.