Blog Image Size

Hello again. Thanks for the great support on my last question. I really love this theme!
How do I make the images I add to posts line up with left and right margins? The images I add from the image gallery seem to resize to a max width 640px, while the Youtube videos size to 677px. How can I make the images the same width as the video content?

The image file I attached shows an example of this.

Thank you!


Can you show me the website address to see the issue in details? So that I can provide you codes for fixing the issue.

Let us know,