If you need a group for a use case, create one in Yammer.

Create a group

  1. Select Create a group at the bottom of the Groups pane.

  2. Select Internal Group or External Group.

  3. Type in a Group Name.

  4. Type in the names or emails of Group Members.

  5. Select Public Access or Private Access.

  6. Select Create Group.

Add information and customize the group's look

  1. In your group, select Settings.

  2. Type a brief statement in the Group Description about the purpose of your group.

  3. To add a photo:

    • Select Add.

    • Go to the picture you want to use.

    • Select Open.

  4. Select a color for the header.

  5. Select a Group Pattern to give your group some design and personality.

Source: Microsoft