Hi,
Did you already try to force it a little? You can do that adding a CSS property to the div where your image is contained, or directly on the img element.
Raw example:
<div style="put inline CSS code here"> ...your content here... </div>
And about the appropriate CSS line I think to remember you have to play with width and height. I say I think to remember because I believe some adjustments may be require because of parent containers layouts.
Example from my creator page:
<img style="border:15px solid white; width: 50%; max-width:100px; padding: 10px;" src="<a href=...here goes a link itch create when adding an image</a>">
You could play with width and max-width I hope.
Some links:
https://www.w3schools.com/howto/howto_css_full_page.asp
https://stackoverflow.com/questions/26033347/display-image-full-size-css
I'd recommend W3Schools to refresh HTML & CSS
https://www.w3schools.com/html/html_css.asp
https://www.w3schools.com/css/css_dimension.asp
I hope this helps a bit!
Good luck!
PS. Sorry for all the edits. Something weird is happening when I add the second code section