You want to send your tweet to someone on twitter in private mode without knowing how to do it. Please follow the article

Or if you want to create a fake tweet from a celebrity like Donald Trump and don't know photoshop. So use WonHowTo's fake tweet generator. A fake tweet to prank your friends will be fun, isn't it?
1. Share private Tweet on the Web
Step 1: On the Tweet you want to share privately, click More (the arrow icon points up).
Step 2: Click on the Send via Direct Message option from the dropdown menu.
Step 3: Enter the username or group you want to share Tweet with, then click Next.
Step 4: Add any comment you want, then click Send to share the tweet in private mode on the message.
2. Share private Tweet via App
2.1. Through Direct Message
Step 1: Click and hold the Tweet you want to share privately, wait until the popup menu appears.
Step 2: Here you click Send via Direct Message.
Step 3: Search and select the username or group you want to share Tweet.
Step 4: Add any notes you want, then click Send to share private Tweets.