Downloading the Program
It's easiest to just visit the Downloads link on the left. Go with the top link if you want the most recent version, but the bold link if you want the better version. For a while, those will be the same, but once there's a chance I could break the program <nervous laugh>, it'll be different.
If the download link has a star next to it, then you want to add the program to your startup programs list. It's hard to explain how to do that, but there's got to be something online about it.
If it doesn't, then either it does that automatically, or (more likely) it's not worth the bother, since there'll just be another version released in a few days anyways.
Using the Program
At this point, there's not really much to use. Just wait three minutes and voila. On Windows or (with any luck) Linux, there'll be a blank system tray icon, which you can right-click for a context menu. Mac users, I'll try to think of something.