How to upgrade the official version of Win10 Preview?

Microsoft previously promised to allow registered users of the Windows Insiders project to upgrade from the Windows 10 Preview to the official version for free on July 29, but the initial presentation was so general that it caused many users to misunderstand.

Today, Microsoft explained the policy of the official version of the Windows 10 Preview Edition through an official blog.
In general, when the official version of Windows 10 arrives, Windows Insiders users have two choices:
1, no upgrade, continue to test user identity;
2, leave the test user community, upgrade to formal Version of Windows 10.
For the first case, Microsoft said that users who choose to stay in the Windows Insiders project will continue to receive updates to the subsequent preview system. The activation of the system is also using the preview version of the Key. Time to experience the new features Microsoft provides for Windows.
For those who choose to upgrade to the official version of Windows 10, first of all, you must ensure that your computer has genuine Windows 7/8.1 installed, so that you can successfully activate Windows 10 after installing it. If the preview system is installed on the user's computer, then you must first roll back to Windows 7/8.1 and then upgrade.
At the same time, Windows XP and Windows Vista users cannot upgrade to Windows 10 for free.