millennial theme - hidden menu with submenu widget

1. Go to Theme
2. Click on the arrow next to the Customizer button
3. Click on Edit HTML
4. Click once anywhere inside the code to enable the search
5. Use ctrl+f or cmd+F to open the search box
6. Search for ]]></b:template-skin> (image 1)
7. Above this line, paste the following code body#layout .hidden { display: block; } (image 2)
8. Save the changes

Image 1

Image 2