Step by step to install Windows Phone 8.1 GDR1

Windows Phone 8.1 Preview The latest version brings an exciting experience that you can not ignore.
Currently, Windows 8.1 product key is still available to developers for testing as Preview. However, the process of registering a Microsoft developer account is a lot easier than with Google or Apple.
So, you can quickly become a developer and use Windows Phone 8.1 in the following steps.
Step 1: Sign up for a Microsoft account
If you do not already have a Microsoft office 2010 product key account, please go to this address to register an email address that is either @ hotmail.com or @ outlook.com.
Step 2: Sign up for a developer account
Go here, then declare your account information to login. Then, select Yes on the popup message.
At the next site, check the request to accept the terms of use, click Register.
Step 3: Install the Preview for Developers app
On your Windows Phone smartphone, just go to Store, enter the Preview for Developers search box to install this app.
Then launch Preview for Developers, then select next> accept> check Enable Preview for Developers> done> done.
Note, you need to sign in to a device with a pre-registered Microsoft  office 2016 product key account.
Step 4: Update to the latest version of Windows Phone
Now that your device is being understood as a developer's device, all the latest updates will come to you. Now go to settings> phone update> check for updates and select "download" or "install" for notifications.
Note, the update to Windows 8.1 product key Preview GDR1 may include multiple intermediate versions. Therefore, you need to update until the device tells you that you are using the latest version.