As a Host, you can create a note or message that gets instantly sent out to all members by going to Network Settings > Members > Message All Members.
Use the available field to write out a short announcement or share an important update. You can highlight the text to see your options for adding or adjusting formatting.
Once your message is sent out, members will be notified either via email or push notification depending on their notification preferences.
Note that while you will not receive updates in your notifications area when Members use the Message All Members feature.