Awake runs as a Quick Tile Setting.
Please add Awake’s Quick Settings Tile icon to your notification tray.
1: Slide down your Quick Settings Tile and click on edit.
2: Find Awake icon. Long press and drag it to the top.
3: Turn on Awake, by clicking on "Stay awake" icon.
If your phone is charging and you turn on Awake, it will stay awake indefinitely.
If your phone is not charging, Awake will keep your phone’s screen awake for 10 minutes.