Build a portfolio with fashion-related photos. Volunteer, if you cannot get a paid gig, purely for experience. Try to create a niche that makes you photos stand out against others in the industry. The more you practice, the better your photos will appear.
Send queries with ideas for layouts to fashion editors and publishers. Draw examples of what you expect to happen and include actual samples of your work.
Network at fashion shows and industry parties with editors and publishers. Hand out your business card and do your best to make a good impression. Do not go too much into detail about your experience; save that for the second time you speak with each other. Follow up with a call to the editor or publisher within the next week.
Apply for a photography internship at your favorite fashion magazine. Work your way up from intern to a full-time photographer.