Okay, so you've decided to stick around and give this thing a try. Be warned, however, that once you get used to gestures it will be difficult to live without them. I take no responsibility for any dependency resulting in the use of this software!
The first thing you'll probably want to do is review the basic options and existing gestures. By default, the right mouse button is set as your primary stroke button. This means that when you hold down the right mouse button and move the mouse, StrokesPlus.net will begin analyzing the drawing to see if you draw a matching gesture. Once you release the right mouse button, the final drawing (and any modifiers, more on that later) will be compared to the existing actions to determine what, or if any, action was matched and execute the corresponding script.
There are quite a few basic gestures and actions configured by default, so take some time testing them out and removing any which you do not imagine yourself using.
StrokesPlus.net has an extreme amount of flexibility and configurability, so take your time and try not to get overwhelmed. The majority of people who use this application only use the most common options and scripts, leaving most of the complexity alone. However, the amount of things possible are almost only limited to your imagination.