To publish products to an Etsy store first ensure you have setup the store account and essential store settings as described in the solution Create A Store In Etsy.
To add the store first login to the App and select Stores from the left-hand bar to show the stores setup against your account. Hit the New Store button to show available store types.
Select Etsy from the listed stores types.
Complete the form that appears with the store domain and your chosen display name.
The store will be added to the list of configured stores. Selecting the new store tile will redirect to a page at Etsy.com to authorize the App to manage product listings on your behalf.
Agreeing to these terms will take you back to the App, now setup to publish products to the store. Products can then be managed within the store and synchronised as normal for Shopify stores.
The Settings from the left-hand bar will show the standard store settings page with the Etsy store domain that has been setup.