Sending Direct Messages From Twitterrific (Mac & iOS)
How do I send a direct message?
Tap the user's avatar on the tweet from the person you want to message. On the user's profile, select the envelope icon. Or tap the compose button and type "d ". There is a space after the "d".
Select a tweet from a user you want to direct message and hit the reply arrow or simply press command-D on the keyboard. If you know the username of the person you want to message click the compose icon and type "d @username". There should be a space after the d.