In SharePoint products, group is a security term. With respect to managed metadata, a group is a set of term sets that all share common security requirements. Only users who have contributor permissions for a specific group can manage term sets that belong to the group or create new term sets within it. Organizations should create groups for term sets that will have unique access or security needs.
Go to Central Administration -> Application Management -> Manage metadata Service applications
Right click on the menage metadata service, then click on new Group
Our group was created like below