In the top right corner, select the Gear Icon (Settings and Configurations). This will take you here:
Within the horizontal navigation bar, select Users. Within the drop down, select Groups. This will take you here:
Updated for 7.0
In the top right corner, select the Gear Icon (Settings and Configurations). This will take you here:
Within the horizontal navigation bar, select Users. Within the drop down, select Groups. This will take you here: