Hi TheREV,
There is no way to add a secondary device for prepaid users but if you are a postpaid customer you can add a secondary device, adding MAC:Address. Unfortunately the only way to make use of the free 10 GB free WI-FI is by using a smartphone or tablet, unfortunately you are unable to use your computer etc.
Have you recently rooted your handset ? If you've probably your handset doesn't support the feature for authentication.