Page builder–rounded box

Hi,

I am using the free version of page builder. It works very well. I have added borders to some of the widgets, but I would like the corners to be round. I have tried some custom CSS that I found here,

.entry-content img {border-radius: 5px 20px 5px !important;}

but that did not work. Is there any way to do that in the free version (2.0.7), theme, Responsive Mobile.

Thanks,

jeff