It all depends on how you want to upload it. If you made a whole new world, then it will be a .sims3 file, and you can simply upload it. If you changed Sunset Valley around, then you should save without playing it (after changing it, of course), and then upload the saved folder entirely, with the 4-5 files in it. To do so, I used WinRar, because it lets me place all the files in a single download.