How to change X-axis in plots of Advanced Design System?

I just finished a small design with Advanced Design System 2008, under AC Simulation I set a Parameter Sweeper to change a D.C. voltage value, but when I run the simulation and plot, the X-axis is frequency, how can I change it to the D.C. voltage I swept?

My design is the attached figure.

I'm not familiar with ADS, but if it's similar to LTSpice then I think an AC Sim will always have frequency on the X-axis. Try a different type of simulation (DC?).