Change Homepage Slider Size – Hero Theme

I’ve been reading through numerous forums and pages about changing the slider size, but I’m not very experienced with CSS and need some specific help to find the right code lines to change.

I’m trying to change the slider on the homepage so the text below can be seen when the page is first loaded up. https://yingc.com/wordpress/

Is there also a way to make sure that the images also stay in proportion and don’t get cut off with a size change? Thank you!