How To Sideload Modern Apps on Windows 8
 

The average Windows 8 user can only download apps that Microsoft has approved from the Windows Store. Windows 8 offers two ways to sideload unapproved apps, which are intended for developers and businesses with internal apps.

These methods cannot be used by the average geek to install unapproved apps from the web. Windows 8’s new interface takes the Apple iOS approach of forbidding unapproved software, not the Android approach of allowing all users to enable sideloading.

Note: This only applies to Modern apps in the new Windows 8 interface, not on the desktop. Windows desktop applications can be installed normally. However, you can’t install any desktop applications on devices running Windows RT.

http://www.howtogeek.com/129535/how-...-on-windows-8/