Adding a CSS class in General tab of the widget

Hi,

I’m trying to add a css class that will only apply to the titles in the widget.

I added this in theme css:

.sidebartitles {
font-weight: initial;
font-size: 17px;
}

and I put sidebartitles in the CSS class textbox in general tab of the widget.

Can you please advise what am I doing wrong and how can I get this work.

Thanks a lot,

Ante

https://www.ads-software.com/plugins/ultimate-posts-widget/