To start a new chat, click the plus icon on the left side panel next to “DIRECT MESSAGES.”
A search panel will open up. Type the name of the contact who you’d like to start a new chat with. As you type, contacts that match your search will appear in a list below. Once the person you’re looking for appears, click their name and then press the green “Go” button. This will open a new direct message chat.
If you want to start a chat with a new contact, click the “New Contact” button in the top right corner.