Reply To: Featured Image Shows Up Huge

[Bidur]

Hello Alison,

Please add the following css inside the additional css section of your customizer;

.page-thumbnail img {
    width: auto;
}
OR,
.page-thumbnail img {
    width: 50%;
}

Note: You may change the width value of your own.
Well you have the option to select the featured image size for blog posts indeed.
1. Go to Dashboard>Customize>Basic Settings>Blog Settings
2. Under Featured Image, select or check the small featured image field.

Best Regards,
Bidur