Yup. You have to resive them.
here's the tutorial For reference, you mention when the page is loading that the recommended screen pixel width is 1025. The image of your trailer is actually 2592 pixels wide. It's not showing as that big because within the html of that page someone has told people's browsers to display it as 488 pixels wide. So a huge file has been squished into a small box. The file isn't any smaller, just that it's displaying smaller.
If your website saw the traffic our site does, that image at that size might crash your server. Eeks!
I would think that whatever digital camera you're using would come with a bundled piece of software that you can edit pictures with. You'll need to use that in order to get those pictures posted here.