I figure that's what all the handwaving about magic tachyons was about: Antiflash (Reverse Flash, seriously?) can now travel back in time and, apparently, Barry will eventually be able to but can't save his mom. As far as why Wells is helping Barry, I thought it was as a guinea pig and a sort of "tension exercise" - the more Wells can learn about and from Barry the more he can learn to apply to himself and the harder Barry gets to beat, the harder Wells is to beat. But that part doesn't really make sense to me after all as Wells seems plenty far ahead of Barry and to know enough even without using himself or Barry as a test subject in any dangerous way.
I will say, though, that I hate the time-travel element that's now in this as it leads to causal headaches that I don't want and don't think the show needs. But oh well.
Aside from that, it was pretty good, if a bit cluttered, and even if we've already seen plenty of Barry/Joe bonding moments and such.