This article only covers the BigCommerce specific setup, for the full setup use  Setting up a new Webstore

Configure BigCommerce API

  1. Log in to your BigCommerce admin portal / backend.
  2. Click on Settings  on the left.
  3. Scroll down to the bottom until you find API and click on Store-Level API Accounts.
  4. Click on Create API Account.
  5. Ensure Token Type is set to V2/V3 API Token.
  6. Type in a name for your connection which should be TWC.
  7. Under the OAuth Scopes ensure the following is granted permissions
    Information & settingsread-only
    Order transactionsmodify
    Create paymentscreate
    Get payment methodsread-only
    Store Locations
    Channel Settings
    Channel Listings
    Store Inventorymodify

  8. Click on Save
  9. You will then be presented with the BigCommerce API Credentials Page.  COPY each of the keys and paste these into notepad as they will be needed later and you can't access these steps again. 

TWC API Key Mapping

When inputting the API keys in the TWC setup please follow these instructions
For store hash, this is best obtained by from your Big Commerce admin URL and is the number and letters after the store-.  So if you admin URL is then your store hash is xf89i49gzt.