In sitewide settings in your dashboard change the text editor option to 'custom' and you will see this line:
theme_concrete_styles: "Note=ccm-note",

Change 'note' to the name of the style and change 'ccm-note' to the css style class name. If you want mulitple do like:

theme_concrete_styles: "styleone=styleone,styletwo=styletwo",

The only thing im not 100% sure about is where the css class style needs to be. either in typography.css or your main style sheet. Its been a while since i used this so cant remember. maybe some else could answer that part.

Yes, it needs to be in a stylesheet called "typography.css".