If you want to send direct messages to someone on twitter, then follow these steps:
>> Login to your twitter account
>> Click on the envelope icon which is at the top of the page.
>> You will find a pop up screen which will show your conversation history. Click on the option “New message”.
>> Enter your message which you want to send and click on the option which says “send message”.
You need to keep in mind that you can send messages only to the person who is following you.