Where do I put the source plan?

Put the source plan in ${basedir}/src/main/plan/ directory.

How do I configure whether to use the maven dependencies?

By default the dependencies included in the car-maven-plugin configuration are used. This allows you to precisely specify exactly which dependencies are included, their version, and the importType. If you do not need this level of control you may wish to use the maven dependencies instead. To do this include an element true true