1, first of all, open AE import material to create a new composite, (in turn, click the menu File - Import - File).
2, and then new composite.
3, in the pop-up dialog box to set.
4, then add the effect (effect-keylight-?keylight).
5, click to select the straw tool Absorb the green color of the screen, then you will see the background becomes transparent, and finally you can fill the new background to make the screen more beautiful.