To connect Big Business to Ecwid you need to log into your Ecwid Dashboard, go to:
https://my.ecwid.com/store/{store-id}#develop-apps
and click Create to create a new app connection. Then copy the Tokens into Ecwid Setup in Big Business.
This Solution tells you step-by-step how to get Tokens. (7088)
To create credentials for Ecwid:
1. Sign in to your Ecwid Dashboard
2. Go to https://my.ecwid.com/store/{store-id}#develop-apps
This link is in docs or just copy #develop-apps and paste after your store-id
3. Click the button to "Create" a new app connection
Copy the Public Token and the Secret Token into Ecwid Settings in Big Business.