Bigcommerce generate oauth tokens
1.Log into the store, using the store owner’s username/password.
2.Select Advanced Settings.
3.Select API Accounts. This will display the Store API Accounts page.
4.Select Create API Account. This will display the Create API Account page shown above.
5.In the Name field, summarize the purpose for which you will use these credentials.
6.In the OAuth Scopes section, select at least the minimal scopes your app will require.
7.Select Save at the page’s lower right-hand corner.
A successful save will display the pop-up shown below, containing the API credentials that your app will need to run authenticated requests – your Client ID and Access Token. (Certain APIs also need the Client Secret for signing.) A .txt file containing the same credentials will (on most browsers) automatically download to your computer. This file also contains the base API Path for your store, preconfigured for the v3 API.
For more deatils click here: https://developer.bigcommerce.com/api/#obtaining-oauth-tokens