1. Have the Right Mindset. Think Like An Entrepreneur.
2. Have a Vision for your brand identity
3. Industry Research. Know Who Your Clients Are
4. Start Small With One to Three Products
5. Design/Import your clothes. This is exciting.
6. Set The Right Prices.
   I get a lot of questions on this so let me elaborate:
   An aspect of running a fashion design business successfully is setting the right prices. Find out the amount that your target customer is willing to pay for your product or service. Then, calculate how much your business would spend on raw material, manufacturing and your time (intellect for your design). This way, set the prices in between the highest prices a customer can pay for your fashion product and your overall cost of production. Make sure that the price you set gives you a decent profit.
7. Marketing. Put Everything On social media or a free Website and promote it
8. Marketing. Talk to retailers.
9. Network. In fashion business,  believe me – your competitor is your friend. They will helps sales ultimately.
10. Get Feedback from customers And Make Timely Improvements

Hope these have been of help. Constructive Comments and Questions are always welcome