Go to Menus -> Main Menu
That takes you to Menu Item Manager: mainmenu
If you want to add a menu item, click New.
In Menu Item: New
If you want to link to an article (i.e. a web page in the hub)
click Articles->Article->Article Layout
Then on the upper right you will be able to select an article, click the Select button.
If you know the name of the article, type it into the Filter. Otherwise click Reset to see all the articles.
Click the article name you want.
Then, on the left type in a Title. The title will be the menu label for the article so you don’t want it to be too long.
Click Save. This will take you back to Menu Item Manager: mainmenu
Make sure that there is a green check mark under published for your article.