First you must download Microsoft Visual C#.
After you have Microsoft Visual C# downloaded, download Laser Interaction. The file name will probably be really weird, so rename it Laser Interaction. Now you will need a laser or IR pen to use it. The first picture is a schematic I made of a simple IR pen you can make. I am using a 100 ohm resistor because I am using 5 volts from a USB cable. You need to have a momentary pushbutton switch on it. I used a normally opened switch so when I press the button, it will click. I also bought a cheap $5 dollar laser from radioshack. I'm sure you can find one cheaper, but I love radioshack stuff.