Congratulations, you have already created your distribution list. What makes it exceptional is the ease with which you can edit your contact list. How can you achieve that? Simply click Contacts in the Navigation Pane, and then double-click the name of the name of the person whose details needs to be edited. Outlook will take you the same screen you used to create the distribution list. While on this screen you can make all the changes you wanted to do on the contact list.
Does the post office sell mailing lists?