For the Write to Etsy connection, you will need to follow a few steps for connecting as below:
1. Once you are in the Stock Sync dashboard, click on the Setup New Feed.
2. Click on Update existing Products in store and click continue.
3. Enter Etsy in the field provided to search the templates.
4. Once searched for the template, click on Export from Shopify to find the Write to Etsy template.
5. Then, choose to Customize the template to set up the feed. 
6. Once appear the file setting of Etsy connection. You need to fill up the necessary fields.
7. Before you authorize your access you should fill up the store name.
8. Then, click the authorize button to continue. Enter your Etsy account credentials.
9. Click Allow access.
10. Once successfully Access Authorized, you click the Next button there to continue with field mapping.
You might need to authorize again if failed to get authorized from Etsy.