how to create node for ecommerce display page?
There is a module Auto Product Display 

This module will do automatically create product display for you.


  This module is created in order to solve that problem. This module can
  simplify the Product Display creation process by providing option the
  create it at the same time with Product creation.
  
  Features
  
  
  Provide the Product Display creation form along with the Product
  creation form. User can fill that form to create Product Display at
  the same time with Product creation.
  That form, which used to create Product Display, will be the same as
  the form when user try to create Product Display manually. So, If
  you have additional fields in your Product Display node type, those
  fields will also appear in the form.
  If the product is referenced by only one Product Display, the
  Product Display content is displayed directly to the form, so it
  will be automatically updated when you save the product.
  If the product is referenced by more than one Product Display, the
  referencing Product Displays will be displayed in list, so you can
  also update the Product Display by clicking the link from that list
  first.
  


If you want to create manually, this will guide you

"Product Display" is the default content type that Commerce Kickstart 1.x creates and it has a product reference field. Technically, any entity that has a product reference field could be considered a product display. Nodes are the obvious product display entity type, and they're privileged because they're the default and standard entity type to use for the front-end display of content. But you could use taxonomy vocabularies, or even users as product displays.

Taken reference from here 

Basically you need to add product reference field field for your node.