Curt, do you mean to apply CSS for the content inside the Admin section? If so, then you’ll have to use a plugin which allows you to append CSS rules to the default WP ones and those set by Baltic Amber themes & schemes plugin (if you are using it).

I don’t know if there any plugins like that, but I made one for my own needs some time ago — called Admin CSS. I have uploaded it for you here: add-admin-css.zip. Unzip, upload, activate and then under ‘Settings’ > ‘Admin CSS’ you can overwrite all admin CSS rules.