Hi,
the farfield calculation in CST is easy and doesn't need an extra farfield probe. You just add the farfield monitor (solve -> field monitors -> farfield/RCS + frequency). You then will see the 3D farfield once the calculation is done. The bad thing is just that you will have to run the calculation again and you have to choose a frequency for the farfield monitor in advance. You can't do that later (not that I know).
The near field was never of intrest for me but I would say that you should activate the E-field and H-field to see the strength of the field near the antenna.
Like I said, I don't think that you can see the results later if you forgot to activate the monitor.