I really liked Brad Miller's (the guy that wrote the FRC library) youtube series, which is mainly about the RobotBuilder tool, but it also shows some basic coding.
https://www.youtube.com/watch?v=k7Pa...lgn vhGObeKzp
Besides that, your next best place to start is the official documentation -
http://wpilib.screenstepslive.com/s/3120