1. How to configure ShippingEasy.
Open the url https://app.shippingeasy.com/settings/stores.
Open the url https://app.shippingeasy.com/settings/stores. And press Edit store settings. On the next page enable Display Product Options.
Read this original documentation https://shippingeasy.readme.io/docs/getting-started-1#store-setup.
Be careful. You should use "https".
ShippingEasy allows you to create several stores in one your account. It's very usefull. Open the url https://app.shippingeasy.com/settings/stores. And press the button Add new.
On the next page select the value ShippingEasy API and write your store URL.
On the next page find API Confiration section and set the value /plugins/shippingeasy/ipnhandler for parameter Shipment Callback path. Save it.
On the next page you will see your Store API Key
It's important. ShippingEasy checks your store URL and registered store URL in its store settings. See the next pictures.