Hi katemegill. The theme default is to expand the image to fill 100% of the content width, with the length being expanded proportionately. Since your image is in portrait layout it gets pretty large. There are a couple of things you can do using css to adjust it. This should be added to a child theme style.css file, the theme Custom css, or a plugin like Simple Custom CSS.
1. Use the default image size of 640×480 and center it
.featured img {
width: auto;
margin: 0 auto;
}
2. Size it manually (change the width as desired) and center it
.featured img {
width: 500px;
margin: 0 auto;
}
Let me know if either of those gives you the results you’re looking for.