Block quotes in post not working

I don’t know how to alter my theme so that I can personalize my block quotes within posts. When I block quote in a post, it doesn’t look all that different than the rest of the post. Is there a plug-in or anything that you would recommend so I can personalize the look of these block quotes in my posts?

Thanks so much! I’m sure it’s something that’s not difficult and I’m just missing it ??