Go to Admin->Menus->Main Menu and choose New. You will see the "Select Menu Item Type" screen.

Under "Internal Links" are sections for all the components we have installed.
Click on Articles and the menu will expand to show all the layouts for articles.

For Menu Type choose Articles->Article->Article Layout.

Enter a title, select a parent menu if necessary.

In the Parameters (Basic), click on "Select" beside "Select an Article".

Find your article and select it.

Save your menu item.

You now have a menu item that points to your article.