In left hand navigation, Click on Appearance > Menus
Select a menu: Main Nav (If not already selected) and Click on Select button.
Adding page in Menu
To the left of the Menu Structure, Click on the Pages tab.
Select the page that you want to put in Menu.
Click on Add to Menu.
Adding Custom Link in Menu
Even if we don’t have a page, we can add a link to the Menu. (The four blogs don’t have a page, they each have a link. (See here: https://mplsheart.org/user-guide/blog/ to know more about blogs.)
To the left of the Menu Structure, Click on the Custom Links tab.
Enter the URL(link) in the URL field
Enter the text that you want to appear in the Menu in the Link Text field
Click Add to Menu button.
Now in the Menu Structure, Drag and drop the added menu item to reposition it in correct location.