Basic Custom CSS Question

Hi-

I’m trying to add a small bit of custom CSS to my page to remove padding on images that are default in the NextGen Gallery plugin. I spoke with the plugin creator and he said the css for single images is .ngg-singlepic. So I placed this in the custom css editor:

.ngg-singlepic {
	padding: 0;
	background-color: transparent;
}

Nothing is changing. I’m not entirely sure what I’m doing. I understand the concept of css but have never really created any, so any help on making this work would be super appreciated.

Also, the website in question is https://www.beatestmusic.com and if you look at the main image on this page, you’ll see what I’m trying to get rid of:

https://betatestmusic.com/?page_id=49