From a Home screen, swipe up from the center of the display to access the apps screen.
Navigate: Settings > Display.
Tap Sleep then select an option (e.g., 15 seconds, 30 seconds, 1 minute, etc.).
To control what happens when the phone is docked or charging:
Tap Screen saver.
Tap Current screen saver then select an option (e.g., Clock, Colors, etc.).
Tap When to start then select an option (e.g., While charging, While docked, etc.).
Tap the left arrow icon (upper-left) to return to the display settings screen.
Tap Display size then select how large or small to make items appear on your screen.
To select a size, touch and hold the green dot then drag left or right to the desired option (e.g., Default, Small, Large, etc.).