This article provides the instruction for installing updates for apps on Windows 8 systems. Windows 8 Consumer Preview users can find out the number of apps that have updates using the Store icon on Windows 8 start menu.
In the above screenshot, the Store icon displays the number as 4. On clicking the Store icon will open the Store section which display the Updates option at the top right corner.
Now you can select the required apps that needs to be updated then click the Install icon.