Fast Stone:
After installation I put the icon on my Quick Launch Bar - easy to get to when you want to use it -

When you click it you will get this in the top right corner of your screen:

Putting your mouse on each icon will tell you what they do. You can capture Freehand, Fullscreen, Active Window, Scrolling Window, etc etc. Has a color picker too.. pretty handy.
Simple way is to click the icon on the right. Checkmark: To Editor
Then when you do a screenshot, the picture will automatically come up in the Editor.. from there you can save it.