If you are new to MATSim, we suggest that have a look at the tutorial "Getting started with MATSim". It will teach you the basics of MATSim and give you an introduction to the code. Once you start writing your own classes that either make use of MATSim or otherwise interact with MATSim, you may be interested in our notes in the Developer's Guide.
In the User Guide, you will find information about how to use MATSim, how to enable special features, and more.
The developer guide
Choose a topic of interest to read more:
We have prepared some tutorials which should help you getting started with MATSim.