Find it here:
On the Slide Show tab in the Monitors group click Use Presenters View
Access Keys: Alt, S, V
Use it to:
Show the full-screen slide show using Presenter View.
This view allows you to project the full-screen slide show to one monitor while viewing a special "speaker view" on another monitor that includes timings and speaker notes.
This feature requires multiple monitors or a laptop with dual-display capabilities.
Other ways to do this:
On the Broadcast tab
On the Broadcast tab in the Monitors group click Use Presenter View
Access Keys: Alt, B, V