|Generally some combination of pressing and holding the control and the alt keys then using the arrow key. Sometimes you have to use the right hand side ctrl-alt keys. Hopefully you have arrow keys that are separate. I call this the lazy hand screen change. You drag your right hand across the keys and the screen rotates. |
If none of that works then you might try a restore point to a day or so ago or see if your video and or screen settings allow you to rotate it.
Hang up and live.