There are a couple of ways to reach someone by sending them a message. I will go over all of them.
Send a private message using Profile Card
Click someone's avatar on the floor, this will open a small interface with a wave and chat. Click the chat button, and the chat interface will open.
Send a private message using People Panel
Open the people panel, in the list; click the arrow beside the person you would like to send a message to.
From the expanded option, click the chat button; and you will be redirected to the chat interface.
Send a private or group message using Message panel
Go towards the Message panel by clicking on the text bubble on the left side of the screen.
- Under "Direct Messages"; select the person you would like to send a message to and the chat interface will expand.
- If you would like to make a group chat, click the '+' button beside Channels, and then "Create Chanel." Give a name to your group chat, decide whether or not you would like this chat to be private; and click create.
After that, you can add all the members you would like to be in the chat.