Make Smooth Scroll work via Custom Style CSS

Dear GP-team,

implemented a great slider plugin (Depicter, incredible tool) and implemented an anchor link. Now I am struggling on how to implement the smooth scroll function from GeneeratePress. I have the option to manipulate the button/link in the Depicter tool with Custom CSS, but I am not sure on how to implement smooth scroll there. It's working with

selector {
background: green;
}

Maybe you can give me a hint here, would appreciate that.

Thanks a lot in advance!