You can store Impossible Sausage just like any meat -- it poses no unique food safety risks.
If sold thawed, the package should have a sticker with a “best by" date (added by the store). For best quality and freshness, we recommend keeping it in your refrigerator and finishing it off before that date. Like any other perishable food, though, the freshness starts to diminish after you’ve opened the package. After the package has been opened, we recommend keeping the package covered up and finishing it by the “best by” date on the sticker.
You can re-freeze Impossible Sausage to use later if needed. To make sure it stays fresh, we recommend it spend no more than three days total thawed once the package has been opened, and that you finish it off before the "use by" date printed on the back of the packaging.