How to open Defender with pre-installed Win8?

My computer is Win8, which is pre-installed in the notebook. Click on the Windows Defender software under the Metro interface. Tip:
“Windows Defender is closed and will not monitor your computer.&##>
Unable to open Windows defender, what should I do?
Generally, this is a pre-installed system with anti-virus software installed, so you don't need Windows Defender, sometimes it will cause conflicts. If you have to play Windows Defender, you can uninstall the pre-installation. Installed anti-virus software, taking Y470 as an example, the pre-installed anti-virus software is Mcafee.
Step 1: Uninstall Mcafee in the control panel, as shown below:

Step 2: After rebooting the machine according to the prompt, enter “> ; Control Panel & rdquo; & ldquo; System Security & rdquo; " Operation Center & rdquo; & ldquo; Security " Click & ldquo; Immediately enable & rdquo;
Windows defender. When enabled, will display the "immediately update" button Windows defender has been started normally:
As shown below: