Hey blueonit,
thanks for your post. In order to use the online shop plugin, you need an online shop from one of our many resellers. Please have a look at our Spanish providers: https://www.epages.com/es/partners/proveedores/
Once you have the shop, you will find the API URL of that shop when clicking on help in your ePages ecommerce backoffice.
Let me know, if I can help.
Malte Scholz
Product Manager
ePages GmbH