Step 1 : Book a domain like abcxyz.com.
Step 2 : Get some hosting or server space for your domain.
Step 3 : Select a developer like shopgoon.com to develop an eCommerce website for you.
Step 4 : Place few test products and set product options, discount, coupon, taxation, shipping, payment gateways, notification alerts etc.
Step 5 : Test it as end user (admin/vendor/customer) and get familiar with your store functions.
Step 6 : Place a nice logo and match your website appearance as per dominant color in your logo. Place few good banners. Fix layout for each pages like home, category, product page etc..
Step 7 : Take a back up of your whole project. Restoring this backup can give your website back along with demo products and all basic setups.
Steps 8 : Remove or edit all demo products and feed it with your original products and categories. Use export/import feature to do so.
Step 9 : Promote it via google adword, email and sms marketing. Start focusing on SEO.
Step 10 : Once you start getting orders, focus on business automation.
Happy Selling !!