Steps To Find Access Token, Store HASH, and Client ID from BigCommerce account

1. Log in to your BigCommerce account. 
2. From the left pane, select Advanced Settings > API Accounts. The Store API Accounts page is displayed.
   
3. Click Create API Account. The Create API account page is displayed.
4. Enter the API account name in the Name textbox and make the selection as shown in the following image for Oauth Scopes:
   

Note: You can find the Store HASH information from the API Path text box.

The Stare HASH is the value between /stores/ and /v3/ in the API Path. That is g3uz5c7jx.

5. Click Save. The BigCommerce API Credential page is displayed that contains Access Token and Client ID.