Unfortunately, the answer to this question is: SLOWLY.
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That's pretty common because they're often the cheapest, most available option. But now you have to make it not-frozen before you roast it. And the thing to know is this: That takes a really long time.
Source: thermoworks.com
A frozen turkey will thaw at a rate of 4 lbs per day in the refrigerator.
1. Keep it in its original packaging and place it breast-side up on a baking sheet with sides so the juices don't get everywhere.
2. Put it on the lowest shelf near the back of the fridge, which is the coldest, safest place for it.
3. Use an instant-read digital meat thermometer to check the temp as it thaws. Be sure to check multiple locations on the bird; the meat will likely be colder near the bone or in the center. You want an even 40-45°F throughout the bird.