There is no network rendering functionality built-in to Terragen at this point. To install a render node, the process is the same as with a regular install, including use of the license key file. The difference is in the use. You can either render an image from the UI or using the command line version. Documentation for command line options are in the /Docs folder of the Terragen install directory.
To render an animation across multiple computers you can either manually assign a range of frames to each machine, or use a render manager like Deadline, Qube, Backburner, etc. A link to some known-working options are on our resources page here:
https://planetside.co.uk/terragen-resources/Distributing the rendering of a single frame across multiple computers requires a bit more effort, but for high resolution and long renders it can be worth it. You need to manually create multiple overlapping crop areas and set each computer to render one of the crops, then manually stitch together the results afterward. Some render manager applications may have functionality to help automate this. Also in most cases with both animation and still frame rendering across multiple machines you will want to use a GI cache to ensure consistent renders. Documentation for that is here:
http://planetside.co.uk/wiki/index.php?title=Terragen_4_Global_Illumination#Rendering_with_GI_cache_files- Oshyan