How do you set the default font?

I am using RoboHelp 11. I have imported an old .HLP and I am converting to .CHM.

I am not able to edit the default, or (none) font in project settings >  CSS Styles > Edit:

Since the Formatting section is greyed out, how can you edit this? I need to change my default font to Verdana. i don't seem to be able to edit CSS in Notepad, either.

The Formatting section is also greyed out in the styles pane for (none):

Thank you