This tutorial assumes you've already created a Facebook account, and are logged in.
Facebook allows you to send private messages to one or more people at a time. These messages can only be viewed by the people involved in the conversation.
To view or send messages, click this icon.
Click a message to read it.
This is where you can respond to the message.
If you want to start a conversation, click the messaging icon again.
Then click to Send a New Message.
Start typing the name of the person you want to contact...
... then select them from the list.
Since we already had a conversation thread with this person, our message was simply added to that thread.
This is the end of the tutorial. You now know how to view and send private messages in Facebook.