Using External Monitor. Want Mouse to move Up/Down, not Left/Right?
Solution 1:
You don't need to worry about Spaces for this. What you need to do is go into:
System Preferences --> Displays --> Arrangement
Drag the icon representing your external monitor to the top of the icon representing your macbook monitor:
You can also drag the bar representing your menubar/dock to whichever monitor you want to be your "main" display.