You've always had the ability to add a new group in the Groups tab. However, now you have the option of creating groups from a search. To do this, simply create a new search or open an existing one. Select the desired users and click on the Select Groups from Search button. Here you'll choose the users. Give your group a name and select the school(s) in which it will be visible. Once the new group is saved, it will be visible in the Groups tab.
If you do not have this feature and believe that you should, please contact OnCourse Support.