On the new distribution group creation page, you set the Display name, Email address, Owners, and members:
Creating a distribution list
You cannot set delivery management (who is allowed to send to the group) on creation, and it defaults to senders within organization only. For many lists, where you want to be able to receive email from the general public, you'll want to change that as soon as the group is created and you can edit it. You also cannot set message approval, group delegation, or mail tips, though you can add a note that will remind you or other administrators what the group is for.
To create a distribution ...
