You may need to be careful how you phrase things to GGL, but this is the process, as I recall it. You first ensure you ignore the email link that's provided (and may well send you a silver card instead).

Your "friend" needs to set up his own BA blue card online, then you ring GGL with his name and number. GGL then upgrade it to a Gold card and they send out the card - typically the process needs to take place between 10 and 24th day of the month due to the mailing cycle they use, if you are UK based. So now is a good time to do this. They will send a welcome email to your "friend's" email address, but maybe your "friend" will switch over the email address (and change PIN) after the card has been sent.

Hope that's clear......