Shutter speed is the length of time that the shutter remains open.  Techniques like light painting and night landscapes benefit from slower shutter speeds (longer exposures), while faster shutter speeds (shorter exposures) allow you to limit motion blur when light conditions permit.

Here's how to set shutter speed:

1. Make sure Manual Controls are enabled (swipe up on the touchscreen, touch the "gear" icon, then from the Menu verify the "Manual" option is checked; touch the blue "X" to exit the Menu).
2. Swipe down on the touchscreen and touch the "Shutter Speed" button.
   
3. To reach one end of the shutter range quickly, repeatedly swipe the on-screen slider toward the left for faster shutter speeds (up to 1/250), or to the right for slower shutter speeds (up to 8 seconds).  For fine adjustments, tap on either of the arrow heads.
   
   
4. Touch the "Set" button. (If you touch "Auto" then your adjustments will not be kept.) 
   TIP: Your manual setting will be confirmed by horizontal lines above and below the Shutter Speed in the upper left.
   
   
   
   
   NOTES: You cannot toggle the ND Filter or see the EV meter unless both the Shutter Speed and ISO Sensitivity are set manually.  
   Conversely, the Auto-Exposure Lock is only available when the Shutter Speed and ISO Sensitivity are not both set manually.