Once you have conquered the HelloWorld example, you should start looking at Box2D's testbed. The testbed is a testing framework and demo environment. Here are some of the features:

• Camera with pan and zoom.
• Mouse picking of shapes attached to dynamic bodies.
• Extensible set of tests.
• GUI for selecting tests, parameter tuning, and debug drawing options.
• Pause and single step simulation.
• Text rendering.

Box2D Testbed

The testbed has many examples of Box2D usage in the test cases and the framework itself. I encourage you to explore and tinker with the testbed as you learn Box2D.

Note: the testbed is written using GLFW and imgui. The testbed is not part of the Box2D library. The Box2D library is agnostic about rendering. As shown by the HelloWorld example, you don't need a renderer to use Box2D.