Hmmm. If I would get into relationship on the internet, I'd probably move to country were she lives. How would I start relationship? I have no idea, really, I wasn't in any relationship for m entire life, sorry...
Ask them out. You could be really forward and just say something like "Can I tell you something crazy?" if they say yes, just be like "I have a crush on you" and see if they feel the same way.