To integrate your GPS Tab account with Chain you can generate a token yourself or reach out to support at GPS Tab and ask for an API Key.
Go to Management / API Tokens from your GPS Tab account
Click on Generate Token
Enter "Chain" as the token name and click ok
You will be redirected to view the tokens. Copy the token for Chain,
Enter the Token in Chain's onboarding page or in the Settings > Apps > GPS Tab; or provide it to support@trychain.com