From what I can see, this documentation - https://www.adobe.com/support/dreamweaver/layout/bg_image_in_table/bg_image_in_table03.htm l
To add a background image to a table, table column, or table cell:
1 In the Document window, select the table element to which you want to add a background image. 2 In the Property inspector's BG field, select the folder icon, then navigate to the image you want to use as the background image.
But unfortunately, my inspector's BG field folder icon does not show up after the table is selected.
Given that DW 8 is more than 10-years old, I wouldn't consider using a tutorial that was prepared using that version. And using tables for layout is definitely not the way to go either. The right way to do this would be to use CSS to specify the background image for any element on your page. That way, the background specification is not part of your page content, but can reside in an externally linked file.
Tell us please what your skill level is with HTML and CSS. It may be that a day spent running through the tutorials at http://www.html.net, or http://www.w3schools.com is all you need to get up to speed. It is true that the more you know about HTML and CSS, the easier DW will be to use...