One more question how do you know which selector is used and/or how do you assign a selector?
The easiest way to see what selector is being used, you can right-click on the title in a modern browser and choose the "Inspect Element" option. It will show you the HTML for whatever you clicked on and all of the CSS that applies to it. If you see a font or font-family rule for the thing you clicked on, that's the thing to use. Sometimes you have to click around a little to find it (i.e. if the font is set on an
a element inside an
To assign a selector via a Typekit Kit Editor (which is the advanced font mode in WordPress.com and also requires a separate Typekit subscription), you need to open the Kit Editor in your Typekit account over at http://typekit.com/ and enter the selector into the kit.
Here's an example of what the selector field looks like over at typekit.com:
Here is a related help document from the typekit.com site: