From the Multiplayer menu select THEATER.
Select SELECT FILM
Select RECENT GAMES. and pick the game from which you want to capture.
Select START FILM to have full control of the film speeds and cameras. Or select CREATE HILIGHT REEL to auto-create a film that fast forwards through the match from your POV and only shows your kills.
Look at the control panel at the bottom to FFW REV and REC and change camera angles etc. Record the segment you want. WHen you stop recording you'll be prompted to name and save or discard the clip. Save it and you'll go to a menu where you select UPLOAD EDITED FILM.
When you back out of the movie and go back to the SELECT FILM menu you then select EDITED FILMS and your clip should be there.
Select the clip and you'll be brought to a lobby where you can START FILM to watch and/or select RENDER VIDEO.
Selecting RENDER VIDEO will make the file for youtube and post it to the blackops 2 eliteTV channel on YOutube (you must sign up for Elite -- it's free and fast -- to participate)
in your Elite dashboard on your home computer you will find a link to the video or search your PsnID/gamertag and black ops on youtube.
Kind of complicated, yes, but once you've done it it is kind of self-explanatory. the menu tree is kind of annoying.
And you cannot post the video to your own youtube channel with your own title and description without some end-around program that captures YouTube video to your desktop as a movie file.