Navigation menu options

Hi

I am having some trouble finding the way to make the menu work as it is most commonly used.

When I add a page under another page that shows in the main menu, I clic on the main page and it doesnt open, just shows that it has a page below. I would like the page to behave as any other, with its content and all. Please tell me how this is done.

This is my demo, im referring to page “diseno web”.

Thanks in advance
Esther