Watch and learned all the Ruby and Rails Courses but still not sure how to create an e-commerce website.

A few thoughts on this:

• There will always be more to a programming language that TeamTreehouse can teach you. But all big languages and frameworks have great documentations that guide you through all functionalities. But even after reading them there is more to learn by looking into Library and Framework code, to understand how stuff really works.
• Practice is always important, because by the time, you watched the last video, you have probably already forgotten some things from the first video. It will take you a few months to get familiar with the the stuff you have learned. Then you will also be able to apply this to new situations.
• Creating a complete E-Commerce website with secure login, payment, stock-management and administration interface is a really big job, and most companies have whole teams to run their e-commerce website.
• You will need more then just ruby on rails to run a big web platform. You should definitely check out some of the HTML, CSS, JavaScript, Databases, and Security Courses here (and also iOS and Android for having a mobile app)
• If you are interested in having a working and secure e-commerce website fast and easy, you should have a look in Content Management Systems, like Wordpress. They bring many functionalities out of the box and a lot more come with plugins.

-> When you want to create it on your own, then just start coding. Learning by doing is the best when it comes to web developing. Create you Controllers, think about what views you need. Create a simple database model on paper, when you think, that it will work then create it in rails and add more and more functionalities over time