First you must define a menu before you can add items to it.
Under Appearance > Menus select ‘Create a new menu’ at the top of the page. Enter a name for your new menu in the ‘Menu Name’ box. Click the ‘Create Menu’ button.
Second thing is adding items to a menu. You can add different link types into your menu, these are split between panes left of the menu you’re currently editing. Select the ‘Pages’ that you want to add by clicking the checkbox next to each page title. Click the ‘Add to Menu’ button located at the bottom of this pane to add your selection(s) to the menu that you created in the previous step.
You can also create a Mega Menu and put sidebars in the menu. To create a mega menu add a page or a custom link to your menu and save it. Then open that menu, and you’ll see a ‘Menu Type’ drop down, that will let you choose a mega menu type. You can add up to 7 columns in a mega menu. Any sub menu of the mega menu will appear as a mega menu column.
In some of our themes sidebar can be added to the menu. Adding a sidebar is easy as adding a page. If you cannot see Add Sidebar drop down list you’ll need to go to ‘Screen options’, and check the Add Sidebar’ checkbox.
After you’ve set up your desired menu, make sure that desired menu is selected. Scroll down to the ‘Menu Settings’ and select location where you want to place selected menu.
If you want to have a onepager page, just use custom links and add a section name with the hashtag in front.
For example, if you have section on your page, that you’ve assigned the ‘about_us’ ID, you can link to it in menu by adding custom link with ‘#about_us’ in the link input field. This will enable the scroll to this section.
Click the ‘Save Menu’ button once you’ve added all the menu items you want.