To create a shareable address group:

Choose Addresses > New Subscription Group...

Type a name and, optionally, a description for the group.

Click the Sharing tab.

If you don't want to allow people to subscribe or unsubscribe themselves from this list, uncheck the "Allow anyone to subscribe to this group" checkbox. If you leave this box checked, people will be able to add or remove themselves from the list, but will not be able to see or edit other members of the list.

Click the "Allow other Direct Mail users to edit this group" checkbox.

Click the Add (+) button and type the email addresses of the Direct Mail Pro users with whom you want to share this group. Note that this must be the email address they registered Direct Mail Pro with. You can see what your registered email address is by choosing Direct Mail > About Direct Mail.

Click OK.