The only thing you need to do to it is heat it entirely throughout. It is likely already cooked fully.
I always put mine in a cake pan or lasagna pan then cover that with heavy foil to seal in the moisture. Then I heat it for several hours in a low heat over. Maybe 250-275. Not enough to make it cook fast or overcook, just enough to get the internal temp up where you need it to be.
If you put brown sugar on it be prepared to know this, brown sugar can catch fire and blaze. If the oven is too high and the sugar doesn't get moist enough then it can actually blaze flames into the stove...did this with a meal once. Scared the frat guys I was house mom for.