Is there a way to make images bigger in the complete post page.

Hi,

On a website i’m doing, the design is like this:
on the pages, you have many posts with an image on the left for each posts and part of the text that all end by ”read more…”.
Then, if you click on the image, on the title of the post or on the ”read more…” you access on a page with the complete post and no more post. I would like the image to be bigger and centered in the complete post page. But I can’t find how.
Is there a way to do it?

Thanks to help, I’m searching and searching for over 100 hours.