no android device found!

hi
i am new in unity
when i am build game for android show this message
no android device found!
*make sure USB debugging has been enabled
*check your device in most cases there should be a small icon in the status bar telling you if the USB connection is up.
*if you are sure that device is attached then it might be USB driver problem for derails please check android sdk setup section in unity manual.
and when cancel windows show this
couldnt find android device
no android devices found.if you are sure that device is attached then it might be usb driver problem for details please check android sdk setup section in unity devial
and show this message in console
what is solution?how package downloaded?

Did you enable Developer mode on your phone? Did you connect your phone with USB to your computer?