Hey, assuming you have a BMC interface set with an IP username and password. Then you also need to have a BMC proxy running on that network (foreman-proxy process with BMC module turned on) and you see such proxy in Administer - Smart Proxies (use refresh feature to see the BMC feature). Finally, you need to ead over to Subnet in Foreman and associate the BMC Proxy with your subnet.
If you have issues, investigate in Foreman and Smart Proxy logs. Enable debug logging and pastebin errors with stacktraces here.