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