1. Swipe from right edge to bring up charms menu
2. tap search, type "power"
3. tap on "settings"
4. tap "edit power plan"
5. change when to dim the display, put computer to sleep, and adjust plan brightness.
6. Click "Save changes" button.
Hope that helps!
You can also hit "windows key + X" to bring up a menu with a bunch of options including the power options.