Managing 365 groups
As the owner of a Office 365 group, you are in control of the membership.
Step 1. Log in to office.com
Step 2. Open Outlook from the list of applications
Step 3. Scroll down to the bottom of the left hand panel. From here click on 'Manage Groups'. This will open up anther window.
Click on Owner. You will see what groups you are the owner of.
ADD MEMBERS
To add members, click on the 'add members' option at the top of the screen.
REMOVE MEMBERS
To remove members of the group, highlight the group that you want to remove someone from. On the right hand side click the X next to the person.