Dell XPS 18 (1820, Early 2014) - Manual (Page 22)

22 │ Using Your Computer
Pairing the wireless keyboard and mouse
If the keyboard and mouse do not work automatically or if the pairing
is lost for some reason, manually pair them with your computer. To
pair the keyboard and mouse:
1 Swipe from the right edge of the display to access Charms.
2 Touch Settings
→ Change PC Settings→ Devices→ Add a
device.
3 Select the keyboard and tap Pair.
4 Once the keyboard has paired, select the mouse and tap Pair.
NOTE: The wireless keyboard and mouse may ship with a USB
dongle. You do not need to install the dongle to use the wireless
keyboard and mouse on this computer.