Adding box shadow to image widget

Hi,

I’ve tried to have a good go at this, and I’m not getting anywhere so wondering if anyone can help.

I am using the Image widget for three images beneath my featured slider on my homepage.

I would like to create a box shadow for each of these images as I have done for my main image using the following code:

‘{-moz-box-shadow: 0 0 7px #888;
-webkit-box-shadow: 0 0 7px#888;
box-shadow: 0 0 7px #888;
}’

I have looked in the widget editor as well as my theme style.css files to see if there is somewhere I can put this but no luck!

If anyone could point me in the right direction/ tell me if this is actually not possible I;d really appreciate it. I’m still learning with wordpress and css etc so I hope this isn’t too much of a silly question!

Here is my site: https://www.theknickerissue.co.uk

The images in question may not appear as they are not ready to publish yet, but you will see what I mean about the box shadow on the main image.

Thanks!