Hi @beckysquire,
I hope you are well today and thank you for your question.
You can try achieving this by using the solution posted in the following topic.
https://colorlibsupport.com/t/size-image/
You can install WordPress plugin on your site as described on the following pages.
https://www.siteground.com/tutorials/wordpress/wordpress_plugins.htm
Best Regards,
Movin