SynaptiCAD ships SystemC help and tutorials with the installation of the software. If you are new to SystemC, you can find this documentation in the SystemC directory:

The SystemC 2.0 User's Guide covers primarily the SystemC 1.0 language features. We recommend that you use the combination of the SystemC 2.0 User's Guide and the Functional Specification for SystemC 2.0 as a User's Guide for the SystemC 2.0 language.