CSS Question – Styling images

Hi there,

This is a real dumb question but I just can’t work out how to style the images in a widget. My website is https://hazyknits.com

On the sidebar, there is a section called ‘instagrams’ and the images are clearly not styled yet. I’d like them to be arranged like the widget above.

Can someone help me with the css needed to format it? I am using the Quest theme and the Instapress plugin.

Thanks,
Hazel