To Correct the Phase manually:
Choose Process > Phase Correction.
If the phase controls are disabled, it means that your spectrum is real. You can make it complex with the command Process > Make Complex.
Choose the peak whose phase is more correct and put a mark on it with ⌘-click(on the Mac) or Alt Gr-click (on Windows); you have chosen what is improperly called the pivot point.
If you are correcting the vertical dimension, create an horizontal mark instead, with the combination alt-click.
If no peak is in absorption mode, first move slowly the big slider at the left of the panel to improve the situation, then create the mark.
Move the big slider at the right of the panel (first-order correction) until the phase of the other peaks is also correct.
If the right slider reaches the end of the run, move the central slider to the position coarse.
If, instead, the phase changes too much, move the central slider to the position fine.
Every time you move the central slider, in either direction, the thumb of the right slider returns to the middle position.
When there is a peak in pure absorption (perfectly symmetric), move the mark over it. Repeat from point 2.
As the correction improves, you should amplify the spectrum with the plus key. The tails of the peaks are extremely diagnostic, because they are anti-symmetric when the phase is not perfectly correct.