May I say, first of all, that you're a beautiful gal, with a lot of potential! I saw your other thread and you look stunning.
There's lots of ways to gain quickly, or more slowly if that's your style. The main thing is consistency, and not letting a high metabolism get you down and discourage you. Consuming things high in calories and in large quantities, of course, will be a great help. Lack of physical activity will expedite the gain as well, though if you want to maintain fitness then you'll need to ingest more calories to compensate. It all depends on the approach you want to take!
Encouragement also helps as well. Again, depends on what you're into.