I am in the military and I dident file last years taxes and if I went into my pay I could print up a w2. What I want to know is can I file for taxes in December and if I can would it be for this year and last year or just last year?

You can't file your 2012 taxes until January of 2013. The W2 you have access to now is for calendar year 2011 (it should say so on it), and you would use it to prepare your 2011 tax return (which was originally due to be filed by Aptil of 2012, but if you got a 6-month exetension would be due October 15).