I understand the confusion! I am not a Mozilla support person, but from my experience, Sync should be called Mozilla Sync, not Firefox or Seamonkey Sync..... If you create an account in Firefox, that account is accessible to Seamonkey. As per the Mozilla instructions, in Firefox you open "Options, sync, add device" and in Seamonkey "setup sync, I already have an account". The text here is a bit confusing because it should read "I already have a Mozilla Sync Account", otherwise you tend to think it implies a Seamonkey Sync account... Then click "connect" and Seamonkey then supplies three fields of characters which you enter in the appropriate fields in the Firefox "add device" dialog. I think it is confusing that in Firefox the server is called "Firefox Sync Server" and likewise Seamonkey offers a "Seamonkey Sync Server" suggesting they are two completely separate, non-connected entities. Hope this helps!