1、打开，设置->我的设备->全部参数
2、看到“MIUI版本”连点7次，在点击的过程中下部会有提示“在点X次就进入开发者模式”。
3、完成2步后，再次打开，设置->更多设置（系统和设备栏内）->开发者选项
4、进入开发者选项后，将USB调试（在调试栏内）打开。
5、插上数据线，将Note4X和电脑连接，选择文件传输那个选项。
6、在电脑上打开终端，输入：adb devices
7、这是Note4X上会提示是否认证的信息，点击确定。
8、这是电脑终端会提示以下内容，表示连接OK：
$ adb devices
List of devices attached
9fc99aebXXXX device
下面是英文教程：
Setting up adb
To use adb with your device, you’ll need to enable developer options and USB debugging:
Open Settings, and select “About”.
Tap on “Build number” seven times.
Go back, and select “Developer options”.
Scroll down, and check the “Android debugging” entry under “Debugging”.
Plug your device into your computer.
On the computer, open up a terminal/command prompt and type adb devices.
A dialog should show on your device, asking you to allow usb debugging. Check “always allow”, and choose “OK”.
Congratulations! adb is now ready to use with your device.