Before all you need to create fonts kit in Adobe Typekit with selected fonts, and only after configure theme,
You don’t need use custom CSS for Typekit. (Just create new kit on Adobe Typekit and copy unique ID.)
Go to Dashboard > Theme Options > General and find Typekit Kit ID. Paste you ID here.
Go to Dashboard > Theme Options > General > General styles and type name of your Typekit’s font here: Base font: custom font family (for example). You need enter font name as it is named in Adobe Typekit