Add a Member to a Distribution List in Office 365

An administrator of an Office 365 organization can add one of your users or contacts to a distribution list/group.

First, open a web browser and go to https://admin.microsoft.com and sign in.

  1. On the left pane of the screen go down and click Exchange. You will be redirected to the Exchange Admin Center.

  2. From here click groups under recipients.

  3. Double click on the group you would like to add members to.

  4. Click membership on the left side of the dialogue box.

  5. Click the '+' sign next to add members.

  6. You can select users and click add then click OK.

  7. You can add them one at a time, or select multiple by holding the control or shift keys.

  8. After adding the users you want to the group click save. 

 

Source: https://docs.microsoft.com/en-us/office365/admin/email/add-user-or-contact-to-distribution-list?view=o365-worldwide