Flex Caption Size

I would like the flex caption on the home page slider to be wider and shorter than it is. I tried changing the code but it didn't work correctly. The white shade disappeared.
What Custom css do I need to use?
thank you

 

Hello,

Paste this code in Custom CSS
Appearance > Theme Option > Styling Option > Custom CSS

Code:

.flex-caption {
width: 700px;
max-height:110px;
}

Adjust its value as per your requirements.