1. Create a new group
Click Account > User Groups
Click Create User Group
Enter a Group Name > Create
2. Add users to the group
Edit the group
Navigate to Users > Click Add Users
You should automatically be in the Users section, but if you're not, simply click Users.
Select the users > Click Add
3. Add a site to the group
Navigate to Site Permissions > Click Add Site
Update viewing/Admin area permissions
Learn more about permissions here: Set up Permission Rules
Your Group is Ready to Go!
This is what your group should look like.