Would appreciate a walk through of how to send a direct message with the twitter node using "D {username} {message}".
Hi,
There isn't a huge amount to walk through. The msg.payload you pass to the Twitter node should be a string with the format "D knolleary Hello Nick" ... where knolleary is the user you want to send the DM to.
You must make sure the Twitter app you register to get the access tokens has permissions to access you direct messages.
Nick
Many thanks, I hadn't appreciated it was that simple, I was looking for too much complexity in the node red help. 
Thanks for the answer but I can not send DM to a user.
where to do that? I mean to get access tokens that has permission?
You have to setup a developer account on Twitter itself
Twitter has instructions on how to do that - Google is your friend 
Make sure you make a copy of all the keys and tokens it offers you, so you can then paste them into the NR Twitter configuration node
NB The user you are sending the DM to must me following you in order to receive a DM from you,
