Remember that Ansys, Cosmos and other types of generic finite element analysis software is just that, generic software. CAESAR II is programmed to do two things:
1. make a (linear) finite element analysis of the system using 3D beam elements.
2. calculate code stresses and compare them with the allowable code stresses.
If you have experience with Ansys and other FEA, you'll probably know something about FEA. To start using CAESAR II you also have to know the piping code as specific input is required.
CAESAR II in itself is not that difficult to work with, but please first study the codes and then CAESAR II, not the other way around.