How do I direct message a friend on Discord?

To send a direct message to a friend on Discord:

Open the Discord app on your device.
In the left-hand menu, click on the "Friends" tab.
In the list of friends that appears, click on the person you want to message. This will open a direct message window with the person you have selected.
You can type your message in the text box and press enter to send it.
The person you have sent the message to will receive a notification and will be able to reply to your message in the direct message window.