Get rid of extra white space in animations

Hello,

I am making some animations, and I have been trying to reduce the extra space that is in the video file. When I change the dimensions as I export it, it seems to shrink, but not get rid of the excess white space. Is there a better way to get it cropped better? In the picture below, I want it to be where the red box is. The smaller picture is when I changed the ratio to 640 by 480 vs the original 1256 by 480. I like the height, but there is too much width that onlyshrinks the whole animation when I make is smaller.

Sincerely,

Dustine