Hello. I would need assistance to add Amazon to my store. 
I already did the Amazon part. I just need to connect it to the store and it is quite difficult.
If you need help connecting Amazon to your store to fulfill Shopify orders from Amazon FBA, this guide shows you how: How to Automate Order Fulfillment on Shopify.
If you’re wanting to import Amazon FBM orders from Amazon to Shopify, the app Codisto does that.
If you’re looking to sync product info between Amazon and Shopify, Codisto also does that. I prefer uploading products to Amazon via spreadsheet though because tailoring the listing descriptions to each marketplace can maximize conversion rate at each place, since the customer and experience is different.