We announced Twitter Kit 3 a few weeks ago, and there’s full detail on how to upgrade from Fabric here. You’ll need to connect your API keys to a Twitter account.
Depending on which platform you are using, there are details on how to request a user’s email address in the iOS and Android sections of the Twitter Kit documentation.
You no longer need to use the form that the Fabric team referenced in order to have your app whitelisted for email access, that information is outdated.