“Napa” Development Tool for Office 365 Apps

The “Napa” Office 365 Development Tools make it easy to start building apps for Office and SharePoint without leaving your browser or installing software.

When we jump to Office 365 and try to install Napa, you might get error saying :
"We need your help to make this app work:
Turn on Developer Feature

This means we need to have a developer site created to use Napa tools.
Now go to SharePoint work space in Office 365.

Once you are on SharePoint Admin Center, try creating a Site collection. Please note that you cannot create a new Public site collection until you subscribe(not available in trail version).