Login to O365 Webmail

Login to O365 Webmail here: http://office365.lboro.ac.uk ‌

Click on the Settings icon (cog) on the top right-hand side of the menu bar.

From the drop-down Settings menu, scroll to the bottom and select ‘View all Outlook settings’ option. This will open a new pop-up box. 

Click 'General'

Click General in the drop down menu of the left hand side of your screen, then select Distribution groups.

Groups

This will display all the groups you belong to and all the groups you own.

Add / Remove

Under groups you own, double click on the group you want to add/remove access on.

Then click on membership on the left. Here you can add and remove members as necessary. When finished ensure that you 'save' any changes