It's actually better to record while you play than from an AHfilm, but it's not hard to do it this way.
Loilo is a free program. Install it and then start AHfilm. You can tell Loilo which program you want to record from. Then load the film you want and expand the film viewer to full screen. You can also preset compression to save space. You will have to experiment to find the best setting.
http://loilo.tv/us/product/game_recorderAHFilm has problems right now for things like engine startups, gun fire, and other things, which is one reason I prefer to record while I play. This is one free method. You can also use GeForce Experience, but then you will also have to find out how to edit videos. If you want to do that just ask and I will post the free editor link.
Repeat topic so you could search for it.
(EDIT): Free
video editor. I don't know how good it is.
