Open your web browser and go to https://outlook.office365.com/ecp/ and log in with your account
Navigate to Options and select Groups. Go to Distribution groups I own and search for your DL on the right. In the Search Results, double-click the DL name.
Select the Membership tab to view all recipients.
To add members to the distribution list, click the "+" sign.
To remove members, select the member name and click the "-" sign.
