How does Win8 get Win8.1 updates through the app store?

Microsoft has been pushing Windows 8.1 updates to Win8 users for free through the Windows Store. It would be best to see free updates in the prominent location of the Windows Store homepage, but if you can't find the Win8.1 update?
Microsoft said that the Win8.1 update may require the latest update support from Windows Update. In addition, Windows 8 Enterprise Edition, Enterprise Windows 8 Professional with KMS Activation, Windows 8 with MSDN ISO and Volume Activation Activation It is impossible to get Win8.1 updates through the store.

Now, the software media editor on how to get Win8.1 update through the app store for everyone to organize a guide, I hope to help some friends:
First, the app store push version description
Win+R Run slmgr.vbs /dlv to see the key type in the description.
Description: Windows(R) Operating System, ********* channel
where ********* represents your system key type. Retail stands for retail activation; VOLUME stands for volume activation (including KMS and MAK); OEM stands for OEM key activation.
Retail and OEM keys can be upgraded via the Windows Store, and volume activation mode must be upgraded with the installation image.
Note: Retail Key activated Pro VL does not push upgrades through the Windows Store.
Second, the installation update KB2871389
Third, Win+R run wsreset, you can view the Windows 8.1 free update in the app store