Hi Heather,
First go to Appearance > Customize > Ambition Theme Options > Background Color there you can see the Main Content option where you can change the background color to black for page content area.
And for font color for that content area go to Appearance > Customize > Ambition Theme Options > Font Color where you can see Content to change the font color to any color you like.
If you have any problem the let us know.
Thank you for using our theme.