How to create single page websites?

Hello,

I am trying to create a single page website with several sections on the same page. Each section is linked to a menu item. For example menu has "Products, Applications, About Us and Contact Us". When the user clicks the "About Us" item the page scrolls down to the "About Us" section.

I tried this with existing themes with the following problems.
1. Menu Items only link to separate pages (not to anchors)
2. Menu bar is not frozen when page scrolls.

Can you please guide me on how to design such a website using zoho sitebuilder?
Is there an existing theme which is similar to such a design?

Thanks