Well, there are a number of helps out there. UnderstandingE has some good videos that discuss how to sell on Amazon as well as how to set up a Magento site.
You might start with YouTube. Go there and search selling on Amazon. There are a bunch of videos about it. I can't attest to the value of the information you'll find there. I expect some will be high value and some might be useless. If you're interested in studying from a paid source I can recommend Jim Cockrum's Proven Amazon Course. I'm not an affiliate for that but I have been a member for a couple years and I've found some selling success with what I've learned there.
For selling on Amazon, I think the most important thing is PRODUCTS, what product you are going to list? and what kind advantage you got for those products?
Generally speaking there is two routes you can take. 'Fulfilled by Amazon' (FBA) 'Merchant fullfilled' (FBM) Each one has its pros and cons. Generally speaking, FBM is more for part timers. FBA is more for full-time professional sellers. FBA requires a professional seller account which costs about $40/month. FBA means that Amazon takes care of the shipping of your products and the customer service. With FBM, you are responsible for the shipping. FBA (known as prime shipping to amazon customers) has higher fees, but prime-shipped products command higher prices and are more inclined to get the coveted 'buy box' which you will learn about. Because Amazon keeps changing the rules, and because a lot of the free advice is from people who have something to sell you; I strongly suggest that you get your information directly from the source, Amazon itself and decide if Amazon FBA or FBM is right for you. https://services.amazon.com/selling/getting-started.html
The professional seller account is not actually required for FBA but you'll probably want the features having that account gives you. And FBA is not known as prime shipping. FBA means Fulfilled By Amazon (FBM means Fulfilled By Merchant). You as the FBA merchant send your products to the Amazon warehouse. Amazon stocks them until they're ordered by a customer. Amazon ships the product to the customer and handles any customer complaints and/or returns. Because the products are resident in the Amazon warehouse they are available to Amazon Prime members, but Amazon Prime is not actually related to FBA. FBA is convenient when you consider the time involved for packaging and shipping of individual products and the hassles sometimes suffered from providing customer service.