Could someone please help with a link where I can find the step to step configuration for adding network devices in icinga2 for monitoring purpose.
I guess you need to give more information about your setup.
Do you use director? do you use plain config files?
If you work over config files - you need to read a little about the internal kitchen of icinga2
if you work with the director - there are other instructions in the official documentation.
For beginners, this tutorial, probably, can give a quick kickstart.
Thanks for your reply.For now my organisation have planned to go ahead with icinga1. So I have installed the icinga1 can you help in knowing how to add a network device (Firewall) in the icinga1 to monitor it via browser.
oh, wow. I would say you better reconsider the decision to go along with icinga1. It had EOL at the end of 2018. So it is insecure to use it.
I cannot help you with this. You may try to create a separate thread with a question about icinga1.