orientation ipad scrren

The simple answer is to rotate your iPad between vertical (Portrait) and horizontal (Landscape) screen orientation.

If you have enabled the Rotation Lock, your screen will remain locked in its current screen orientation. The Rotation Lock is accessed from the Control Centre.

To expose the Control Centre, swipe downwards from the top-right corner of the screen - shown here with the Rotation Lock active. Tap the highlighted icon to remove the Rotation Lock:

Some Apps do no not support both screen orientations - and will force the display to either one or other orientation. This is an App limitation - and is not a fault of the OS.