There's no built-in syncing (that would require accounts, servers and all sorts of scary stuff).
Using DropBox or similar is the way to go. There's logic in the app to detect when the file on disk has changed. If this happens after your last local save, it will auto-reload the one on disk. If it happens when you have local unsaved changes, it will ask you if you want to reload or not.
Sadly, this currently only works on Windows, as the Mac/Linux version of wxWidgets file system monitoring code were broken at the time. I should really fix this some time :)
I occasionally use it myself on a Mac, and just got into the habit of quitting the app after using it to avoid and conflicts.