Trouble displaying background image in css file



I have created a div and I want to put background image in so that I can work easily over picture.

Here is my coding

header { width: 1200px;

height: 500px;
background-color: azure;
margin: auto;
background-image: url (http://"www.and so on")


I have tried variations but no success.

I am pulling this image from my files stored in one drive. I can use same image when placing in image tag straight into html file.


Could you post full html + css code?