If it were me... and you just Got To Have the freezer space....I'd leave it frozen unless the packaging is starting to break down.
That said, if you Just Must Can it.... thaw it completely, then cook as if fresh, according to the directions from the canning book.
Remember, even canning it, it will still have a definite Shelf Life, and must either be used by that point, or thrown out. I'm not up on all that, so you'll have to ask some of the "seasoned veterans" around here about that.
You also have the option of cooking it thoroughly, then re-freezing it. I often precook sausage and bacon in large batches, freeze on cookie sheets, then bag. When we need some for a breakfast, we just take out what we want, no waste, and no leftovers.
Best of Luck, and let me know how it turns out,
Kathy
P.S. - You can send a few jars of sausage my way.... Hubby would LOVE to have some....