There are three way to send DM.
1. Send new message from the profile screen
2. Send the message from DM screen
1. Open DM screen from Accounts screen.
2. Add DM screen to the tab bar.
3. Select an account.
4. Tap the icon.
5. Swipe up the icon.
3. Send the message from the swipe shortcut
1. Add the DM button in Settings screen.