Hi Boris,
The easiest way of finding the right class is to inspect the element with your Chrome Dev tools. If you right click on the element in the page you want to give that background image, you will see its class. This is what you place in front of your CSS example like:
.loginpage-image {
...
}
On another note, your CSS annotation for the background is not correct, it should be changed from url(img/’Appbackground.png’); to url(‘img/Appbackground.png’); the quotes should be around the entire file path.