Open the TikTok app
Tap Inbox at the bottom
Tap the message icon or a chat thread
Tap the plus icon or New message if available
Search for the user you want to message
Select the user
Type your message
Tap Send
If you cannot message someone, check their privacy settings
Make sure you follow each other if required
Make sure direct messages are enabled on your account
If you are under the age limit, messaging may be restricted