String break next line and frame around image

I have two problems that I am sure can be solved through css, but I am not sure exactly how to do that. I am a newbie and don’t know a lot about creating custom css for widgets.

1) For one of my widgets I would like the string image to always appear on the next line. How do you change the css to do this and where do you change the css?

2) I would like to put a double border around the image for one of my widgets. How/where do I add the css to do this?

I am assuming the css to add the border would be:

img {
padding:1px;
border:1px solid #021a40;
}

Thanks for any help. Much appreciated.

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