How to make use of a green screen in final cut

-Start with the footage of the original shots of the person with the green screen background.
-Go to effects --> video filters on the final cut menu.
-Click the option Key (blue/green screen)
-Drag to the chosen clip.
-Change the key mode to green.
-Play around with the balance,colour levels, edge feather and so on, till you get a suitable background.
-Optional to change the film to black and white (generally easier to work with when using green screen)
-Move and shrink or increase the size of the character/object.
-Use the motion key frame to animate it.