Custom coding - editing content html

[visualguy]

I am struggling to edit content of my html page. I need to edit source tag for an image within my html page to a image uploaded under the image folder.Within Edit Html/CSS, all I can see is html/css files for the theme. I just cannot find the body content html of the page on the left side menu. I can see the page preview below though. I am not sure what am i missing here.

[Adam7]

If you're just adding an image to your site it's probably much simpler to just add an image element to the page, then upload your image to that.

[daybreakdoula]

Within the main website editor page, just go to:

Themes -> and then at the bottom left "Edit HTML/CSS"