How to change the font on the Appointments page, and also change the font and width of calendar in t

The font used to show "Month, Year" titles on my appointments page is illegible. The same font shows up above the calendar for the widget in my sidebar. How can I change the font style and size of these?
Also, I want to change the width of the calendar on the sidebar widget... how would i go about that?

Thanks in advance for your speedy assistance.