You can't then. One way from here on out is to turn on automatic downloads. Go to settings, store, auto downloads ON(both devices). Now when you download an app/music/books etc it will download on the other device. If you want to match apps from before, just go into store and purchased....to download.
Ok, well I went to do what you just said, and there was no need to do so. I already had both devices ON. They should have communicated with each other up to this point. That being said, I will go into the store like you recommended and have them sync it and pose more questions to them. I better write them down too! Thanks!