You can edit Groups and Distribution Lists in Outlook applications and in the Outlook Web App (OWA). As long as you are an owner of one of these, you can add and remove members are required.
Distribution Lists allow users to send messages to a group of recipients simultaneously by using a single email address. They do not have further or additional features like Groups do (see below).
Groups allow users to send messages to a group of recipients simultaneously via a single email address but also include further features such as a shared mailbox, shared calendar, shared OneNote notebook, SharePoint team site, and more.
Ensure you are logged in online with your appropriate account and go to https://outlook.office.com/people/group/owner
Ensure you are logged in online with your appropriate account and go to https://outlook.office.com/ecp/MyGroups/PersonalGroups.aspx