Follow the below mentioned steps to create a new API account in your BigCommerce store and generate API keys.
Step 1: Login to your BigCommerce store admin and click on the left menu: Advanced Settings.
Step 2: Click on the sub menu API Accounts as shown in the below screenshot.
Step 3: Now click on Create API Account button as shown in the below screenshot.
Step 4: You will see a screen like below screenshot. Add any name of your choice in Name input field.
Choose the Orders and Products permission like in the below screenshot. And click on Save button at the bottom.
Step 5: Now copy the Access token and enter in the app.
Also please note that Shop URL is the admin URL of your store.