Follow instruction here:
http://hyatthotels.hyatt.com/content/partnerlandingpage/en/goldpassport/mlife.html
However, I was not able to process the match automatically after clicking opt-in link. Many other had also experienced the same issue. Some was able to make it to work after a few tries.
Instead, I sent an email to customer service at M Life (memberservices@mgmresorts.com)/ Agent was able to confirm my Hyatt status and grant M life gold tier to me manually