Simple Steps to Follow for Enabling Windows Defender in Windows 8 :

1- First Type Windows Defender on the Search charm from Start Screen and when the Windows Defender App appears Click on it .

2 - Now Click on the SettingsTab.

3 - Under Settings Check on Turn on real-time protection (recommended) and Click on Save Changes.

4 – Done !  Now you can Click on close.

Scan your PC for Spyware and Viruses :

1 - First go the Windows Defender using search charm from the start screen.

2 – From the Home tab, Select the Quick, Full or Custom Scan option and Click on Scan now .

3 – Now Windows Defender will start Scanning your computer and inform you if any threat detected.