widening the sidebar for widgets on pachyderm

Hi, I am migrating from wordpress.com and am setting up a selz widget on my sidebar in pachyderm. I am completely self taught and have managed today to work out how to change the colours on my site using css. However anything else at this stage regarding css I feel is way beyond me. I need to widen my sidebar as it is ridiculously narrow and my image for the selz widget isn’t fitting in it. Can someone help me? Site is https://www.soulsisterwisdom.com
Thanks