Slide Images Too Large

I have a new blog I am in the process of building. I am using your Blue Planet Theme (which I like a lot), but cannot figure out how to make the images on the sliders smaller. Regardless of how much I scale them down, the height and width are way too large. Any words of advice?

There is not much to look at now, but just in case it can help, here is the URL for the site.

https://blog.nwascore.org