Find the article you wish to archive. Click the article "edit" icon to open the article for editing. Scroll down all the way to the bottom. It should look like this:
Option 1:
If you would like to hide the article entirely, change state from PUBLISHED to UNPUBLISHED.
Option 2:
If you would just like it off the front page and back where people can still see the information in the article if they wish, leave it PUBLISHED and uncheck the "Show on Front Page" box.
If you leave an article published, it will be accessible via the SEARCH box.

Option 3:
Change the Access Level to Registered, so it will only be seen by those Registered Users who log in.
Be sure to click the "save" button!