Download and Install ADB or Fastboot on Windows Computer.

Install ADB or Fastboot. On this guide we will show you how to Download and Install ADB or Fastboot on Windows Computer, to start this guide you can visit Android Studio via this link. On this website you can download the Android SDK. which will give you the latest updated version of adb and fastboot. You can explore this page by scrolling down to the bottom of the page and find Other Download Options>SDK Tools Package, then find the right version for your Windows Operating System. While waiting for the download is complete, you can create a folder in drive C:\ called SDK. for an example (C:\SDK).

Now following this guide to install ADB.

After you successfully download the SDK zip, now you can extract it into your C:\SDK folder.
Navigate to

C:\SDK\android-sdk-windows

Then, open SDK Manager.exe.
In SDK Manager you need to install the following packages:

Tools> Android SDK Tools, Android SDK Platform-tools
Extras> Android Support Library, Google USB Driver.

Once installation finish, you will see a new folder created on drive C:\SDK.
One of the folder will be appear platform-tools.
Now you can open the platform-tools folder, then you can see fastboot.exe and adb.exe.
This folder is your fastboot folder.

How to check your ADB or fastboot correctly installed.

Open a command prompt from within your fastboot folder.
To start this command prompt just hold shift + right click, select open command prompt here.

Install ADB or Fastboot on Windows Computer
Now type,

adb version

The result, It should return your device serial number, if so, adb is working.
Now test your fastboot by connecting your device to your PC while booted into the bootloader.
How to reboot your device into bootloader ?

Power Off your device.
Then press and hold power + volume down (it's should work on most android device)

Then type.

fastboot devices

The result, It should return your device serial number, if so, fastboot is working.

How to Boot device into Bootloader.

If you not sure using physical button on your device to boot into bootloader, you can use this tips.

Make sure your device is Power Off
Then, connect your device to the computer.
Open your fastboot folder, then run command prompt from it.
Now type.

adb reboot bootloader

Now your device will reboot into bootloader.

How to Boot device into Recovery.

You can boot your device into the bootloader (see above), use the volume button to scroll through the options and use the power button to select the recovery mode option
Or use this following command.