Hello,
Internship is definitely a good start. Time duration of internship depends on where you intern. It can be of 3 months , 6 months or even a year. Internship takes you a notch higher in gaining some quality experience. Learn that being a stylist would do no good to you if you have no work. Fashion industry works on recommendations. During internship make sure that you show yourself well. Interact with as many people as you can. Your contacts might help you later in fetching some good work. Setting your foot in the industry would definitely take some time. It entirely depends on your skills and capabilities. Its not gonna happen overnight. Just take one step at a time. Learn the very intricacies of design. Be inquisitive about learning new things.
Good luck