This example builds on the One Link - One Component example and adds parameters to the component, using the lib/fastmavlink_parameters.h tool box.
The example implements a component, which sends out a HEARTBEAT message at intervals of 1 Hz, and listens to incoming HEARTBEAT messages from a flight controller or GCS (you need to select) and sends out a "Hello World" STATUSTEXT message as response. In addition it reacts to the PARAM_REQUEST_READ, PARAM_REQUEST_LIST, and PARAM_SET messages.
In order to check its functioning, you can connect to a GCS like MissionPlanner.
See the Arduino sketch arduino_parameters.ino for an implementation (I have tested it on a STM32F103 bluepill).
Please inspect the sketch, and especially the comments. The usage of the lib/fastmavlink_parameters.h functions and tools should be self-explaining.