NO ONE TOLD ME THEY CHANGED THE SITE! I've updated the instructions and will update the video ASAP.
1: Go to: quackit.com
2: Click the Top Dropdown menu labeled 'Background Code'
3: Scroll past 'Background Color' to 'Background Image' and copy the HTML code to the left of the example.
4: Paste this somewhere you can either copy again or where you're about to post.
5: Open a new tab to Google, find a background you want, click on it, and copy the image URL by either
Right Click > Copy Image URL
(while hovering over the image)
or
Press 'view image' and copy the URL in the address bar.
6: Paste this address in the code you copied AFTER the part of the code that says
Url(
Between the ( )
There will be some text inside the () already just delete/paste over it.
7: Type what you want it to say between the < p > < / p >, where it says "The image can be tiled across the background, while the text runs across the top."
Hope this helps! Video again below: