Hi,
If your Customers access the Portal link from your website you can update the link you have currently to the one that is given to by navigating to:
Customize -> Portals -> Get sign-in page web address... (on the new Portal you created)
Copy the URL that is provided.
Or if they come from an Email that is being sent out from your Method account, you can update the hyperlink on the template being used. Head over to Home > Email Templates - choose the template being used and update the hyperlink within the Body with the URL from Get sign-in page web address...
- Mortaza