In previous versions of Windows, you could simply hold the Shift key and right-click on an application to run it as a different user, which was useful for running multiple versions of an application at once. In Windows 8, it works a little different.
Enabling the Run as Different User Option
Press the Windows + R key combination to bring up a run box, type gpedit.msc and hit enter.
Now you will need to drill down into:
User Configuration\Administrative Templates\Start Menu and Taskbar
On the right-hand side you will see a setting called Show “Run as different user” command on Start, double click on it.
Now switch the radio button from “Not Configured” to “Enabled”, then click on the OK button.
Now we will need to force the policy to take effect on your PC, to do this press the Windows + R key combination, when the run box opens the following then hit enter:
That is all there is to it. Now you can easily run applications as a different user from the Start Screen.