it may depend on the transport, you may deploy the IM Gateway Plugin or connect pyMSN as a component to it.
Do you add it by just installing the files?
yes, just put the gateway.jar in the wildfire/plugins directory. jar available here.
once gateway.jar is installed, from your jabber client select the “Service Discovery” option and register with the transport/s (this is where you specify your Yahoo!, MSN, AIM uid/pwd).
for gateway.jar see above.
If you want to install pyMSN then you first need to get Python installed with the libraries needed by pyMSN and this may be tricky. So you’'re much better off with the gateway.jar