Widget font size

I know how to change the widget title size but I can’t figure out how to change the text size of the widget content, such as within a simple text widget. I feel like I’m asking something that should be screamingly obvious but for some reason this one eludes me. Thanks for any help. Here is the site link: http://testsite01.writelife.net/