How can I code images into the background of my online store?

To start this off, I know nothing about coding and have a site I have to get running soon. Knowing this I was looking for a way to code in images to the background that look like this

I know how to create this image but I don’t know how to add it to the background in my Shopify store.

Where on the page are you looking for it to be the background? Send a preview link or store link so we can better assist you

recubu.com on the mobile view everywhere you see it in images is where I want it