I just got mine as well. My agent sent me a letter with information on what to do next but it's in pdf and won't let me copy/paste. It says to send it to the Visa Evidncing Unit in London:

Visa Evidencing Unit
Migration Branch
Australia High Commission
Strand London WC2B 4LA

Send by registered post (special delivery silver pouch recommended for citizens in UK) and that it takes about 3 days to turn around. You need:

-2 unused pages in passport
-cover letter stating what you request
-contact details
-copy of grant letter
-pre-aid self addressed silver pouch for return (keep number off that for tracking purposes of return)

I think that covers it. You can always contact the Evidencing office to double check.