[help] Automatic Image re-sizing

You will want to explore the Media Settings page in the Admin panels of WordPress. wp-admin/options-media.php

Crop thumbnails is the checkbox that cuts off pictures.

The sizes you put in the other fields determine how each picture is resized during the Upload process. In fact, there can be four or more copies of the picture, as resizings are done, if necessary, for the Thumbnail, Medium and Large (there is also Full Size, which is the original picture).

Not knowing whether your web site uses the Thumbnail, Medium or Large resizing, I cannot tell you which of the Sizes needs changing in that panel.

I made it already set to 800×600 but it doesnt resize the video when you on the site, it shows up resized on the gallery in wordpress but when you look on the site it is cropped out

When you said “video”, I assume you mean a still picture, as in .jpg or other format.

When WordPress makes multiple copies of a still picture during upload, only one gets cropped: the Thumbnail. If you don’t want that, then turn the option off in Media Settings. But that only changes how newly-uploaded pictures will be handled.

The size and cropping you see on the web page depends on how the page is coded. In the coding, you can ask for Thumbnail, Medium, Large and Full Size.