Learn how to use photoshop. If you don't already have it, go out and get it and learn it. Search the net for photoshop tutorials, that will get you started.
Join deviantart.com. There you can get inspiration and get feedback on your stuff.
Depending on how good you are, whether you're just starting to get an eye for it, or you just have a natural touch, it could take you anywhere from a year to ten years or more to actually become succesful in fashion photography.
Where you live is also a big factor. If you live in a hick town in the middle of nowhere with no modern culture, theres a good chance you will never get anywhere. I would suggest moving to a big city. There not only could you get noticed but there's just more events, people, etc to shoot. You need quality material. You need to have something people want, something different you know? Unique.
But again, if you're just playing around with your friend right now, all you can do is practice. I began doing photography 5 years ago and its amazing to look back at my work and see the improvements. Good luck