This document will walk you through managing members of groups which you are an owner.
Login
1. Go to outlook.office365.com and login
Options
1. Select the settings gear in the top right corner
2. Select options in the drop down
Other
1. Select Other on the left
2. Select Go to the earlier version
Groups
1. Select Groups on the left
2. Double-click the group you are an owner of on the right
Membership
1. Select Membership
2. This field is the current members
3. Select the + or - to add or remove selected users
4. Be sure to click save before exiting the current window