From OpenCart 2.0+ you will have the option of the Etsy marketplace in your OpenBay Pro market list.
To install and register:
Click the plus icon (+) to install the marketplace
Click the pencil icon to go into the marketplace dashboard
Click on the register icon, this will open in a new browser tab
You need to register for your OpenBay Pro account (or sign in if you already have an account)
When you are redirected to the register page enter your store URL (e.g. www.mystore.com) and agree to the terms.
You will be sent to Etsy to login to your account and confirm that OpenBay Pro is allowed to access your store
An OpenBay Pro Etsy account will now be created for you. Go to your browser tab for your OpenCart admin area and click the settings icon.
Copy the API details you have been given into the matching fields and press save.
You now need to go back into the settings and click on the Sync settings button. This will get all of the latest options from Etsy.
Your install and registration is now complete. Additional options will be displayed in the OpenBay Pro Etsy dashboard in your OpenCart admin area.