To create a group navigate to Admin > People > Groups. Here you will see a list of groups that you create and make a new one by pressing

1. You will be presented with a box where you can type the group names that you want. Create multiple at once by adding a group name per line. Or copy and paste in a list of names. 
2. The new groups will now be on the list, press on the name of the group to open the details. 
3. Now you can invite users to the group, and set them as members or admins by pressing the 3 verticle dots by their name. 
4. You as an Org admin can assign content or the group admin can too

Don't worry if you need to change the name of a group you can do this. It is also super easy to close the groups when they are no longer needed. On the group's list when you navigate to  Admin > People > Groups you can select groups you wish to close by checking the box on the left and then pressing