Formatting in Text Widget

I have looked at previous forum posts on this subject and tried the suggestions without success (including formatting the text on a WP page and cutting from the text view and pasting it in the widget). Some of the HTML works but not the strong tag. Can I achieve bold in the text widget? I do not know CSS.

The text “Header Image:” in the central footer widget is what I want to make bold. See https://redrockraku.com/local-art-galleries/