Hi Kepler,
The free version of the Technology Preview does not allow animation. You may pre-purchase a Terragen 2 license which will allow you to use animation functions for $299 US ($200 US if you are a registered owner of Terragen 0.9). Once you have purchased you will have unrestricted access to the current animation functionality which consists of keyframing for almost all available settings (the A button next to most settings controls keyframes, but is disabled in the free Technology Preview).
- Oshyan