Welcome to Android Central! Can you give us more details? Are you talking about the Google Now Launcher? Or just the Google Now widget on the TouchWiz launcher?
If you're using the Google Now Launcher, that's a completely separate launcher from TouchWiz. The way you set up TouchWiz gets saved with the TouchWiz data, but doesn't get carried over to a new launcher (unless that launcher has an import function, like Nova Launcher does). So if you installed Google Now Launcher, it's up to you to set up the homescreens the way you want them. Since all launchers are going to be different from each other, you may not be able to set it up exactly the same way you had it on TouchWiz.
If you just want the Google Now function, that's already available on the Google Search app--you don't have to install Google Now Launcher for it. Just go back to TouchWiz, and to bring up Google Now, press and hold Menu.