Is this what you are after?
In this quick example i have added a box-shadow to the hover image:
Using the inspect tool i have looked through the code of my website and found the Hover image that we are looking for -
Here is a Link to more information on using the Developer inspection tool if you need it :)
Then once i have found what i am looking for i can create CSS that targets it:
This is a Red box but i did it for visual impact to help
I hope this sets you in the right direction :)
All the best