You should upload the files (HTML and images) within the public_html
folder (or inside any folder in public_html).
To call your web page, for example, yourpage.html, if this file is inside your public_html folder you can call it that:
If you want to display an image (yourimagen.png) from your yourpage.html file, save yourpage.html and yourimagen.png files within the public_html folder, then HTML code that you should write in your yourpage.html file is as follows:
<img src="yourimage.png" alt="alternative text" width="100%" height="100%" />