You can control what appears in the navigation menu at the top of your site by going to the Dashboard and selecting Appearance > Menus from the left-side menu. That will bring you to the Custom Menu editor.
Under the “Edit Menus” tab, click the link that says “create a new menu.” Start by giving your menu a name in the “Menu Name” field, then click the blue Create Menu button. This will create an empty menu with fields called “Menu Structure” and “Menu Settings.”
To the left of the “Menu Structure” area, you will see the four types of items that you can add to a menu: Pages, Posts, Custom Links, and Categories. To add your required posts to the menu, click the Links option from this box to display the “URL” and “Link Text” fields.
Under “Menu Settings,” check the box for “Primary Menu” to make this custom menu display as the main menu at the top of your site. Note: Depending on the theme, the top menu may be titled something different than “Primary Menu.”
When you’re done editing a menu, be sure to click the blue Save Menu button or else your changes will not be saved.