It's fairly simple, you just need to copy/paste the save file into the correct location:
Vista/Windows 7: C:\Users\[username]\AppData\Roaming\LaxiusForce
XP: C:\Documents and Settings\[username]\Application Data\LaxiusForce
(Assuming C:\ is the directory that your Operating System was installed upon.)
If you can't navigate to that location, then the folders are likely hidden. On XP, go to any active explorer window and click "Tools -> Folder Options -> 'View' Tab -> Show hidden files or folders". Not sure about the other Operating Systems offhand.