1. Go to your menu (joomla menu)
2. Change 'Menu Item Type' to 'External URL' (see image) and add the target id of your div (step 3) in section 'Link'.
Don't forget to add '#'!
3. Now you need to add the div with your target id in your content
Repeat this for all menu items (use different id's as target) and include all divs to your content (article, module, ...)
P.S. <body data-spy="scroll" data-target="#t3-mainnav"> was already added by you...
Thanks for your reply Eugen. I was trying to add active class in menu item when someone scroll to specific section. I am converting my OnePage bootstrap theme ( http://wingthemes.com/demos/html/matter/ ) to T3 Joomla Template in Localhost. BTW, i have added this feature by a third-party jQuery plugin.