How to create an App-Specific Password for your Apple ID account

Step 1: Sign in to your Apple ID at https://appleid.apple.com/.

Step 2: Under the “Security” section, click “Generate Passwords”.

Step 3: Enter a label for the password. In this case use “Application Loader” for the label.

Step 4: Click “Create”.

Once you have created the label, Apple will automatically generate the app-specific password tied to it.

Credit : https://learn.appdocumentation.com/en/articles/1651188-how-to-set-up-your-app-specific-password