change width and height

Hello,

I really like the flipbox with image and want to use it, but it is too big for my website. The website isn’t online yet, so I can’t show it. Can you tell me how to change the size of the flipbox? I have looked in the .css file, but I am a nitwit and don’t know how to change it. Any help or a pointer in the right direction is appreciated. I checked the other questions and answers, even tried the suggested custom css, but nothing seems to work.

Kind regards Judith