Once you record and press stop. you have saved a segment.
if you record again from the game your watching it adds it the original segment. and then when you quit you can upload however many segments attached together as one video.
I've got that far, but you then have to go to callofduty.com/theater sign in (having pressed render in the thater menu in game) and you can get your video onto youtube that way. Except that callofduty .com is a treyarch website and a piece of shit, I cant log in or sign up or do anything because the website is so bad and i'm voilently tilted because my tomahawk show as soooo coool!!