Hikvision GUI 4.0 Change Camera on Live View

Go to the system icon at the top (Looks like a cog)
Go to "Live View" on the left
Go to "View" on the left
Choose the video output you want from the "Video Output Interface" dropdown at the top.
Click on a box to highlight it in blue
Double click on the camera you want in the list on the left to put it in that location on the screen
Click "Apply" when done