I am not sure if Dynatrace has support for WebMethod broker as it is a bit of an older technology and I believe was planned to be replaced back in 2012.
That being said, deploying to monitoring would be the same as with any other technology. I would be curious to what you see if you deploy the OneAgent on that host.
If you already have Dynatrace setup, then all you'll need to do is deploy the OneAgent on the host that is running WebMethods broker. Instructions on this can be found in your tenant under the "Deploy Dynatrace" section in the left side menu.
If you have not yet setup a Dynatrace tenant or deployed any agents here is a bit more documentation around that: https://help.dynatrace.com/get-started/introductio...