1) Go to File->Open... and choose an particle environment to play with.
If this is your first time try to change skin conductance or heart rate variability you may wish to start with a "_Trainer" par file. These trainers are more simple graphically, but show very clear and responsive displays.
2) Read the "About this Environment" window to learn what your goal (target) is.
To open this window in the future go to "Settings->About this Environment..."
3) Watch the changes on the screen (and in the background music) respond to your state changes.
You can also customize the environment, or press Ctrl-N to randomly change the images.