Here is a tutorial to create a group with your office 365 acount.
Steps
1.- Enter to your account
2.- At the upper corner of the window, there is an icon. Click it. And also the YAMMER button.
3.- Click the ‘Create a group’.
You’ll be directed to this page.
4.- Choose a name for the group you want to create. The page will automatically tell you if that name is available
5.- Then, add the people you want to be in that group.
6.- You can add more friends.
7.- And also you’re allowed to make the group visible for everybody, or make it private.
8.- Click the CREATE button
And you’re done. You can personalize it if you want to.