How to style image within the_content.

Hello community,

I would like to organize the_content in my index.php in a way that I can control the image size…
My loop always display the first post’s image. Therefore I need to style it to keep the consistency of the blog.

Would it be an option using the_post_thumbnail and set the_content to do not display the post’s firs image?

here is a visual -> https://www.antoniodigitalmedia.com/wp-content/uploads/2012/10/example.png

Thanks