In versions prior to Windows 8.1, it was possible to hold down the Shift key while right-clicking the shortcut to a Command Prompt to find the option to launch using different credentials. Using the new “Modern” interface with Windows 8.1/Windows Server 2012 R2, this option is not present.
One method to again use this feature is to add a shortcut to the Command Prompt to the task bar on the Desktop. Using the old method of holding down the Shift key while right-clicking the shortcut should display the selection.