How to decrease the humongous font for Holder main text

Hello, I have a couple of Holder installs right now and the main text (the default is "Holder" but I changed mine to Mother Me Softly) is HUGE. How do I decrease that? I assume it's an edit to the CSS file but I need some guidance as to how to do that.

Also, how do I make the content less skinny? I would like the option of making it wider. Or is everything so skinny so it will fit on a mobile phone screen?

Thanks!!

Trish