4 corner correction with touchpad or iphone

Hey, its my first time using my PPM without my remote, as i have forgotten it at home while visiting a friend.
So i don’t really get how to do 4 corner correction with the touchad.
what am i supposed to clock when i move the curser on the corner and how do i move it than?
Can please someone give me an explenation.
If there is any way to control it with ipone it would be very helpful as well.

Thanks in advance!!