Screen orientation

Hi there,

To unlock orientation within app (E.g. watching landscape videos in youtube) You must swipe up from the bottom of your screen to access control center, and tap the orientation lock icon, which is a padlock with an arrow around it. If you are trying to view the whole UI in landscape, such as your homescreen, this is only available on the larger, plus devices.

Here is a link with a little more information:

If the screen doesn't rotate on your iPhone, iPad, or iPod touch - Apple Support

Swipe up from the down of the screen to access Control Center and click the lock button