From what I have gathered, some of that information is in the new novels that have been published since they declared all novels prior to the acquisition by Disney as non-canon.
For example, I know a couple of the novels follow the aftermath of the destruction of the 2nd Death Star, including the battle that resulted in all of the crashed ships on Jakku in episode 7.
I'll still see this movie and enjoy it, but I kind of wish that I didn't feel like I'm missing out on the back-story that is contained within the novels. Twenty years ago I would have read all of them, but at this point in my life I just don't have time for it.