Hold the Command key and then the "L" key on a Mac.
Hold the Control key and then the "L" key on a PC.
Or on either platform go to the "View" menu and choose "Layout Mode".
All of this assumes you are working in a solution that is using standard menus.
This gets you to Layout Mode (which I think you might be meaning)
If you really mean Layout Setup, then once in Layout Mode go to the "Layout" menu and choose "Layout Setup".