It's pretty straightforward

:
- Plug the flash drive into a USB port on your computer
- Open the folder for it (it will either come up with an option to open it directly, or you'll need to go to the 'My Computer' folder and select it)
- Drag and drop the files you want to transfer from the folder on your computer to the USB flash drive folder
- Eject/unplug the flash drive from the computer
- Turn on the computer you want to transfer the files to
- Plug the flash drive into a USB port and open the flash drive folder
- Drag and drop the files from the flash drive into a folder on the computer (or wherever you want to put them)
- Eject/unplug the flash drive... and the files will now be on the other computer.