Hi inavarrorubio, and welcome to SaleHoo.
Online business, no matter where in the world, is essentially the same. That said, the differences between them can vary dramatically, depending on the market you are dealing in.
My advice, start with a well thought out business plan, exactly as you would do if starting a more traditional offline store front. Developing a comprehensive business plan will create a road map for you to follow.
It's something that many overlook when starting an online business, and I think that is a mistake. Do the planning now, and you will find your business will benefit from it in the long term.
Good luck with it : )