Thank you all for your advice. After posting here, I called the grocery store and did a basic internet search. TheIncredibles! was correct, not to cook it frozen. But the store and the internet advised me I could thaw it under cold running water for approximately two hours.
I followed this advice and gentled boiled the tail in salted water for 8 minutes.
It turned out perfectly. It really was a huge tail compared to the ones I have had at a restaurant as a surf and turf menu.My DH and I split this and a 6 oz fillet with pasta, creamed spinach and crescent rolls. It worked out to about $10/serving which I think is pretty good!