How to adjust dimensions of homepage slider in PHP or CSS files

Hi,

I would like to change the dimensions of my slider to 1500 x 250. The slider in the backend is listed as “Full-width Slider images are 1500×560 pixels.”

I went into the header php and changed the dimensions of the slider though this did not actually change my webpage.

Is there a way to adjust the code to change the dimensions of my slider.

I don’t know a ton about coding or websites so I’d really appreciate the help! ??

Here’s my site: https://www.archaeoadventures.com/

Thanks so much!

Cheers,

Genevieve