You can position your menu relative to an element in your blog's header when using any Theme. The "Aeros" Theme already contains a default menu that displays the pages of your blog. In this example we have positioned our menu above the default menu in order to replace it and display a more stylish menu that contains more options as items and also subgroups.
The menu, is positioned by placing the ID of the header tag (in our case a DIV) in the "Custom ID" property under the "Element Anchor ID" options.
These are the settings for the Main Menu Group's "Positioning" property:

This is how the menu will look in your blog's homepage:

Click on the image to view the example live