How to adjust image size

Hi! I was wondering if anyone could help me adjust the image size I’m using as the “main photo” for the lightbox. Here’s a link to the page it’s on: https://ampedforeducation.org/lightbox-test/

I need to scale down that huge photo – the size of the lightbox that opens when you click that image is fine.

Also if it helps here’s the code I’m using: [wp_colorbox_media url=”https://ampedforeducation.org/wp-content/uploads/2014/11/jeff-bio1.jpg” type=”image” hyperlink=”https://ampedforeducation.org/wp-content/uploads/2015/01/Jeff-website-final-1-edit.jpg”%5D

Thanks in advance for any help!

Sarah

https://www.ads-software.com/plugins/wp-colorbox/