Sharon:
My first question would be whether you want buttons to share the email message or buttons that allows the user to follow your social pages? The only real way to "share" an email is using the Forward to a Friend token. Marketo's social buttons cannot be used in emails. For "follow" buttons, you basically just use graphics for each of the social pages you want and link them via URL. You could set this up as a snippet or make it part of your email template. Hope this helps.
Mike