@Tarek-H You are right, but with one missing part. You also need to perform frame transformation to take into account different camera orientation (if not using the default forward facing) and align 0 degree heading (otherwise you will see the vehicle facing east at startup).
We also have a non-ROS implementation in Python in part 4, so you can jump to that first to have a quick up-and-running system, and maybe come back when you feel adventurous with ROS.