I had to search, because I couldn't figure it out either. Two things: they changed how you activate it, and gestures are disabled by default even if they were enabled in 9. That may not be required for multi-window to work, but I was used to using it. To turn that on, just search for gesture in settings and you can turn it on (I set to both buttons and gestures). Then, to use multi-window, you have to get to card/task switch view, then press and hold the title above the app you want to split, and select multi-window. Why can't you run Waze and Signal Check at the same time? Do you mean in split screen (multi-window)?