how to pass custom parameters to a locust test class?

You could use like env <parameter>=<value> locust <options> and use <parameter> inside the locust script to use its value

E.g.,
env IP_ADDRESS=100.0.1.1 locust -f locust-file.py --no-web --clients=5 --hatch-rate=1 --num-request=500 and use IP_ADDRESS inside the locust script to access its value which is 100.0.1.1 in this case.