As of my last knowledge update in September 2021, WHMCS does not have an integrated feature for automatic currency rate updates. To achieve automatic currency updates, you may need to rely on third-party services or scripts.

Here's a general outline of how you might set up automatic currency rate updates in WHMCS using an external service:

1. Choose a Currency Exchange Service: Select a reliable currency exchange service or API that provides currency exchange rates. Some popular options include Open Exchange Rates, Fixer.io, or various free and paid API providers.

2. Obtain API Key or Access Credentials: Sign up with the chosen service and obtain the necessary API key or access credentials. These will be used to authenticate your requests to the API.

3. Create a Script or Integration: Develop a script or integration that fetches currency exchange rates from the chosen service using the API. This script can be written in PHP or any other programming language you're comfortable with.

4. Set Up a Cron Job: Schedule a cron job on your server to run the script at regular intervals. This ensures that your currency exchange rates are kept up to date.

5. Update WHMCS Database: Use the script to update the currency exchange rates in your WHMCS database. You'll need to access the WHMCS database and update the relevant tables with the new rates.

6. Testing: Test the script to ensure it's working correctly. Verify that the currency rates in WHMCS are being updated as expected.

7. Automation and Monitoring: Monitor the script to ensure it continues to function correctly. Set up logging or notifications to alert you if any issues arise.

Remember to consider any legal or compliance requirements related to currency exchange rates in your jurisdiction. Additionally, always have proper backup and version control procedures in place when making changes to your WHMCS installation.

Please consult the documentation of the chosen currency exchange service and WHMCS for the most up-to-date information and best practices.