You can access the navigation menu to edit it and make the required changes in two ways. Here is how:
Navigation menu settings in the Website menu
Hover over the Navigation section in the top horizontal bar menu to activate the Navigation editing menu.
Navigation menu settings in the header
Hover over the top horizontal area of your website page so the blue line appears. Click on the stacked line icon to access the Navigation settings menu.
Continue managing the navigation as required. Once done, click Publish to make your changes live.