Email group members from the Admin side or from the Public page. At this time, communication is limited to email, but we have some big plans for inner-group communication.
From the Admin Side
Go to your group and select Email all members.
You can also email all members of a group type. Select the group type then Email all members.
To send an email to a more specific set of people, use the filter bar.
There's not a way to add an attachment to an email; instead, add the file to Resources and point people to that resource.