You catch more bees with honey. Put Botmill in the subject line
Here's a quick overview:
1. Download Arduino 022, and install drivers for arduino MEGA 1280 or MEGA 2650.
2. Download Sprinter, or some other RAMPS compatible firmware. Google Sprinter GitHub.
3. Open the firmware source code in arduino IDE and edit the configure.h file. Pay particular attention to the XYZ print dimensions. Set them to mach Botmill. I'm not familiar.
4. Upload the firmware to RAMPS. Close Arduino IDE.
5. Download RepSnapper. Connect to the serial port listed for the RAMPS (This is a USB to Serial Interface, in case you're wondering)
6. Go to the interactive section, and see what you can control.
Best of luck!