css – How can I upload an image for background use using the Theme Editor in WordPress?

I’m learning WordPress from the book WordPress for Dummies. The author says to open the theme editor then use the style.css sheet. I uploaded the image to the twentyseventeen image folder via FileZilla. She gives this example to add a new background image and change the color to white:

background #FFFFFF
url(‘images/newbackground.gif’);

then she gives other property examples like
background-repeat: repeat-y;

I wasn’t able to change the image using the code the author gave. Where to I have to place this code and how to make this change.

I’ve used the following code in the footer.php template to add category archives to the homepage:

?php wp_list_categories(array(
‘style’ => ‘none’,
‘orderby’ => ‘name’,
‘show_count’ => true,
‘hierarchical’ => true,
‘depth’ => 1
)); ?>

So I know how to add code but I don’t know how to add the examples she gave for the background image.