1. Login to BigCommerce.
2. On the left side of your BigCommerce Dashboard, click Advanced Settings.  Note that this option is only shown for users with “store owner” permissions.
3. Click API Accounts, and choose Create API Account (V2/V3 Token).
At this point the API Path will be displayed – you will need to make note of this API Path.
e.g.
API Path https://api.bigcommerce.com/stores/abcde12345/v3/
Where abcde12345 is the store hash
4. Enter a Name for the app/integration, such as FeatureIT
5. Under OAuthScopes, define the permissions
You will need to define
Content – Read permission
Customers – Read permission
Orders and Order Transactions – Modify permission
Products – Modify permission
6. Click Save.
At this point – after successful save – a pop up window will be displayed.  It will contain API credentials – Client ID, Client Secret, and Access Token.
Also, a .txt file containing the same credentials will (on most browsers) download to your computer.