Asus TX300CA - Manual (Page 58)

58 ASUS Transformer Book E-Manual
4. Select a device from the list. Compare the passcode on your
ASUS Transformer Book with the passcode sent to your chosen
device. If they are the same, tap Yes to successfully pair your
ASUS Transformer Book with the device.
NOTE: For some bluetooth-enabled devices, you may be prompted
to key in the passcode of your ASUS Transformer Book.