Click the "Groups" tab on the left hand side bar to open a drop down menu.
Press "List Groups" on the newly opened menu.
This brings you to a List of all Groups you have administrative power over.
Next to each Group name is a green box that says "Edit" in it, click this to open the edit menu for the desired Group.
This opens a screen where you can change passwords, grant and restrict services.
Once the settings have been altered, press "Edit Group" at the bottom to save your changes.