As long as you are the owner of a distribution list, you can edit the membership by:
Typing the name of the distribution list in the "To" field of a new email message, right clicking on it and then clicking on "Open Outlook Properties"
While the properties are displayed, click on "Modify Members"
From here you can click on the name of a person and hit the "Remove" button if you wish to delete someone.
Or, if you wish to add someone, click "Add"...
Find their name in the Global Address List & double click on it
Then click OK to close this screen, OK to close the previous, OK to close the previous.
Done.