I suggest that you start from PFC2D, because the 2D version has a simple code compared to 3D. The manual of PFC is a good source for learning. Many classic examples are also illustrated in the manual.
PFC documentation can be accessed by opening either PFC 2D or PFC 3D. After opening the software, Go to... Help--> Help (if you want to understand different commands and basics (or Examples if you directly want to see how to apply the commands to specific cases)