How about reading or watching one of the tutorials?
Displaying derivatives (optional)
To display the vorticity in the flow, select Plot -> Derive parameters/ modify data. Select Vorticity in the upper pop-up menu. You can smooth the data by enabling the check box next to Smooth data and dragging the slider a bit to the right. You can change the frame of reference by subtracting the free flow velocity from all vectors. In Subtract flow, enter "-0.2" in u [m/s], and click Apply to all frames. You can also calculate the average velocity of several frames. In Calculate means, enter "1:end" in the field Used frames to calc mean and click Calculate mean vectors. Now, an additional frame will be automatically added to your session. It contains the mean velocity field. All masks of the frames you used to calculate this average will be combined. Vectors will be orange in the average frame, if more than half of the original vectors at that spot were interpolated before.