Select the object you want to array first, then (with Shift) the object you want to use as the axis. As you would want to make a parent.
RMB and choose "Circular array"
All the settings are in the "N" panel in the "Item" tab. You have to have selected the new empty axis object to see them.
!!! Do NOT delete the empties or remove the array modifier!!!
If you want to get rid of it, select the axis object again and click on the "remove array" in the "N" panel
It should make more sense when you watch the intro video.
If something doesn't make sense, don't hesitate to ask.