Green Screen and Chroma Key

For the news screen banner that I downloaded there was a green screen as the background. The green part of the video I didn't want, instead I wanted to just have the banner along the bottom of the screen, and then behind playing another clip that would show the imminent disaster that was about to happen.
I began researching how I could get rid of the green screen on the internet, and was directed to the Chroma Key effect.

The Chroma Key effect is works in the same way a colour mask works on Photoshop.

I searched for chroma key in video effects, and then dragged and dropped it over onto the breaking news banner video.
I could then go to the effect control panel to the video and using the colour tool in the chroma key, could select the colour match tool to select the green of the video. This then worked by making all the elements of that video of that colour transparent, and in turn then allowed for any video underneath to show through.

The edge of the banner still had a slight green edge but by using the similarity option and dragging the number up and down was able to remove the green edge completely. 

After using the chroma key effect the layer that I would place underneath would show through. This is exactly the effect that I wanted to happen and I was very happy with the outcome. It allowed me to fit the disaster into my trailer and appeal realistic due to the news banner and make it seem as though it was everyday current life.