Actually "designing" fashion is only a small part of the apparel industry. In order to be a successful fashion designer, it is important to have a skill set that goes well beyond the design aspects of fashion. Although I can not discuss all aspects of the apparel industry in this blog post, I would like to give you a few hints in regard to the garment manufacturing aspects of the industry.
Here are a few resources that may help you find clothing manufacturers that can assist you with producing apparel and fashion accessories.
First, I would suggest you visit the clothing manufacturer section on Apparel Search. From there, you will find clothing factories, trim suppliers and apparel manufacturing contracters such as sewing facilities.
If you can not find enough clothing manufacturers from the links above, you may want to use the search engine at the Apparel Manufacturer website.
By the way, before fashion designers select clothing factories they should also have experience with pattern making or higher a professional pattern maker.
You may also want to check out the How to Become a Fashion Designer website.
As always, you should also join in the discussions at the Fashion Industry Network if you are interested in learning more about fashion design, clothing production, or any other issue relevant to apparel.