You can start a discussion with whiteboard, and invite members to view and annotate.
Desktop:
1. Open the Conversation.
2. Hover over to the ' + ' icon next to the send message... field at the bottom of the conversation.
3. Alternatively, you can Click on the 
Files icon on the top right corner, then click the Add button.
4. From the list of options shown, choose/click the option Whiteboard.
5. Use the different kinds of whiteboard tools (text, draw, image etc...) provided to create and discuss over the whiteboard with the members of the conversation.
Mobile:
1. Open the Conversation.
2. Tap on the ' + ' icon next to the send message... field at the bottom of the conversation.
3. Alternatively, you can tap on the Files tab on the top, then tap the +Add button.
4. From the list of options shown, choose/tap the option Whiteboard.
5. Use the different kinds of whiteboard tools (text, draw, image etc...) provided to create and discuss over the whiteboard with the members of the conversation.