HFSS-Wave Port and Lumped port assignment

Hi all,
I couldn't understand how to determine a waveport's or a lumped port's direction.
Can anyone experienced in this tool give me detailed information?
I know it should be from lowest to highest voltage. But don't know the direction of the arrow represents which field? or where to assign it? I'm very confused.

Thanks and best regards..

You should define an integration line to specify where the voltage difference is expected to be maximum. This line is used to calculate the port impedance. Apart from this, you should select "Polarize E field" option if you want to align the E-field direction with the integration line direction.