Android - Building Beta Problems.

Hello everyone. So I want to upload the game to my mobile but I've got a small problem.

(Im using a Macbook)

I've followed this steps:

1.Downloaded Android SDK(done)

2.Plugged the Device(android file transfer popped up) *Device is a LG Optimus G

3.Switched Device to Developer Mode & enabled USB debugging.

I keep getting an error : "No device found." (But the computer has access to the device with file transfer).

I just downloaded the SDK so its up-to-date. What am I missing?