How to Change Screen Orientation in Windows 8 and 8.1    Information This tutorial will show you how to change the orientation of a screen.
Source: Eight Forums

Change Screen Orientation of Display in Screen Resolution Settings

1. Do step 2 or 3 below for how you would like to open Screen Resolution.

2. Right click or press and hold on an empty area on your desktop, click/tap on Screen resolution, and go to step 4 below. (see screenshot below)

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3. Open the Control Panel (icons view), and click/tap on the Display icon.

A) Click/tap on the Change display settings link in the left pane, and go to step 4 below. (see screenshot below)

Click image for larger version

4. Select a display (ex: monitor) that you want to change the screen orientation of. (see screenshots below step 5)
NOTE: If needed, you can click/tap on the Identify button to have the display number briefly appear on each display to help know which one to select.

5. Click/tap on the Orientation drop down menu, and select the orientation mode you want, and click/tap on Apply. (see screenshots below)

Note   Note
If this is a tablet, then you could also check or uncheck the Allow the screen to auto-rotate box to turn on or off screen autorotation.

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Click image for larger version

Click image for larger version

6. If the selected screen orientation looks good to you, then click/tap on Keep changes. (see screenshot below)
NOTE: If not, then you could either click/tap on Revert or wait 15 seconds to undo the screen orientation change to go back to what the screen orientation was prior to changing it.

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7. If you like, repeat steps 4 to 6 for any other display you wish to change the screen orientation of. 

8. When finished, click/tap on OK in the Screen Resolution window to close it. (see screenshots below step 5)

Source: www.eightforums.com