Linking accounts is just a matter of using the same username/password in the game as on the website - there is no special option to do this manually, it just happens! This also works retroactively, so for example, say you play Clones and you complete the first 10 levels, but you haven't registered on the site yet. The submitted stats are on the site for your profile, but they aren't linked up to a registered user. Then you decide to finally register on the website so you can post in the forums, upload packages, and publish avatars etc. When you enter your username and password in the options menu in Clones, all your stats for that profile will be then associated with the new user account on the site. Pretty cool huh?