Step 1: In the Posts tab of the Teams view, press Ctrl+F6 until you hear: “Start a new conversation.” Press Spacebar. The focus moves to the message compose box.
Step 2: To expand the compose box to access more editing options, press Ctrl+Shift+X. To collapse the box, press Ctrl+Shift+X again.
Step 3: Type your message. You can also add attachments or even emoji, stickers, or memes to spice up your message. For more information, see Add an attachment, Add an emoji, and Add a sticker or meme.
Step 4: To send a message, press Enter.