We are currently not offering a direct integration to Amazon, eBay, or Walmart, however, it is possible to send the orders to Gelato via Shopify.
Workflow
Amazon/eBay/Walmart <-> Shopify <-> Gelato
Create all products in the 3 platforms
Once an order is placed on Amazon/eBay/Walmart, it goes to Shopify and then to Gelato
When the order is updated (e.g.: tracking link generated), the information goes from Gelato, to Shopify and then to Amazon, eBay, or Walmart
Apps
For the whole process - Product creation & Order workflow - you can use 2 apps:
The integration is based on third-party apps with no relationship with Gelato, which is not responsible for the results.
Tutorial