To add additional pages, posts or custom links to your main menu,
Please go to Appearance > Menus from the dashboard menu.
Using the dropdown menu at the top, please select 'Main Menu.'
Navigate to the Add Menu Items on the left-hand side. Here you can add a page, post, category, event category or custom link to your menu.
Add the items you wish to add to the main menu, and drag and drop them to the location you wish they display.
When you are happy with your changes, navigate to Save Menu to finalize the changes.