The Primary Metric Control is located at the top left of the Analysis Screen. It is labelled 'I want to improve'.
In Ipiphany your Primary Metric acts as your goal, it tells Ipiphany what you are trying to achieve. Set this first so that Ipiphany can provide you with correctly targeted insights.
To set a Primary Metric simply:
Click on the control
Choose an attribute
Choose a function to apply to that attribute
By default only score or numeric attributes are displayed. To select a categorical attribute click 'Show Categorical Attributes'.
If you would like to reduce the value of your selected attribute (Call Time for example) then set 'I want to Minimize this'