Hi Mima,
You don't have to 'transform' anything.
All you need to do is to go to your Account page, download LR into your new computer, as well as the license key.
If you need to retrieve your files from your previous computer, then pls see this thread where I just answered the same question:
http://forum.brillkids.com/little-reader/little-reader-question/msg25189/#msg25189