I want to use a pixhawk 4 with rover model... but i don't know how to start help me please

I bought a pixhawk 4 and GPS package and made a RC car with them.
I use ROS2 foxy in Ubuntu 20.04 and follow this guide (ROS 2 User Guide (PX4-ROS 2 Bridge) | PX4 User Guide).
So I download PX4-Autopilot package and build. (https://github.com/PX4/PX4-Autopilot)
I upload firmware named px4_fmu-v5_default file with using QGC.
And then I don’t know what to do next step…

The PX4 documentation is generally the best place to start for new users. If you’re not sure how anything works, it’s usually a good idea to sit down and read through it to help figure out what area you need to look at in more detail.

I’d suggest having a look here, which provides instructions to set up and use different vehicle types.

Good luck with your rover.