Log into Office 365 and open Outlook
From the bottom left of the screen select Groups.
Click on the arrow next to New and select Group from the list.
Select the option Next from below the Standard Group and then enter the details for your group. When you have done this and set the privacy settings select Create at the top.
You can then add members to your group, start typing their name into the box and they will appear on the list click on them to add them to the Group. When you have added the members you want select the add button at the top.
Your group is now ready to send emails to or share documents with.