adjusting widget location on cover page in wordpress

I am new to WordPress so maybe it looks foolish for you guys. I have attached the image,

http://ift.tt/1YvUd44

what I need is to move that "book a cab"button to move upward, but when I tried to give margin to a button , the button stays same and the cover starts expand.

what I tried already:

margin-bottom:100px;
margin-top:100px;

kindly help me to move this button centered n the background image

via Chebli Mohamed