Unlike many themes you do not need to edit any code to disable the featured image at the top of the post in Divi. However it is quite difficult to find the settings if you do not know where to look.
How to disable the featured image in Divi
Go to Divi -> Theme Options -> Layout -> Single Post Layout -> Disable “Place Thumbs on Posts”
Now your blog posts will not have a featured image at the top of the post and you will be able to add the image inline in your text where ever you would like.