Don't worry, they're not long; in fact, two of these new featurettes are just set tours given by director Bryan Singer. But four of them contain new footage from the movie, and the video above explains how Wolverine's psyche is sent back in time!
This answer is, oddly, that Kitty Pryde can send people's minds back in time. That doesn't make a lot of sense with her ability to phase through solid objects, but to be fair, it's the X-Men — the comics have had far more egregious inconsistencies than this. Although I can't help but think it's a shame Brett Ratner killed Jean Grey off in X-Men 3, because then DOFP could have introduced her daughter Rachel Summers, who was the one who actually sent Kitty Pryde's mind back in the original comics.
Actually, as a psychic, why isn't Professor X the one doing the mind transfer? Wouldn't that seem to be his bailiwick? Doesn't that make more sense than giving Kitty Pryde this inexplicable power? Oh, whatever. At least the new footage is looking good:
And here are the two pure set videos:
[Via Latino Review]