Right click on the running agent to get the menu. There you can enable TCP/IP. Leave the default port. Next you'll need to mess with extensions (probably), but you should be able to connect and do something like:
Agent.DisplayText("Goodbye Cruel World")
Chris R Mead
The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.
Check the silk test help guide for remote and it outlines 3 different methods. The most simplest way is to start the agent on the remote machine and make sure the network is enabled as chris has mentioned. Then open up the options> runtime dialog on the host machine and set the Agent name (generally the name of the remote machine running the agent) and then enable the network to TCP/IP. Make sure the appstate for the testcase is set to none. Try it out. Good luck!!