sillypad on "[Theme: Spun] Change font in posts"

I want to change the font in my posts. I installed the google fonts plugin and don't see any option to select the font when I'm editing the post. I also installed the CSS plugin and tried using this script to change the font but it hasn't changed anything either. Is there another option? What am I doing wrong?

I went to Appearance - Custom CSS Manager - pasted this:

body {
font-family: Tahoma, Verdana, Arial, Helvetica, Futura, sans-serif;
font-size: 16px;
padding: 0;
margin: 0;
}