When you get a new device and start up Windows 10 for the first time, the antivirus protection that comes installed with the device is your default security app. However, Windows Defender Antivirus is pre-installed and ready for you to use at any time.
If you want to use Windows Defender Antivirus, uninstall all of your other antivirus programs and Windows Defender Antivirus will automatically turn on. You may be asked to restart your device.
If you have Windows 10, you can't get Microsoft Security Essentials. But you don't need it, because you already have Windows Defender, which provides the same level of protection.
In the search bar, type Windows Defender.
If you're using Windows 10 Anniversary Update, pick Windows Defender in the results. If you're using Windows 10 Creators Update, pick Windows Defender Security Center. You'll be able to check your computer and your level of virus protection.
Windows Update downloads updates for Windows Defender Antivirus automatically to help keep your device safe and protect it from attacks.